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 Filed Pursuant to Rule 424(b)(2)​

 Registration Statement No. 333-263258

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PROSPECTUS SUPPLEMENT

(to Prospectus dated March 3, 2022)

Up to 1,000,000 Shares

Common Stock

This prospectus supplement describes our Dividend Reinvestment and Direct Stock Purchase Plan, or the Plan, and the shares of our common stock, par value $0.01 per share, to be offered for purchase under the direct stock purchase feature of the Plan. The direct stock purchase feature of the Plan is designed to provide new investors and existing holders of our common stock with a convenient and economical method to purchase shares of our common stock. American Stock Transfer & Trust Company acts as the administrator for the Plan (the “Plan Administrator”).

Key aspects of the direct stock purchase feature of the Plan include:

As of the date of this prospectus, of the 1,000,000 shares of our common stock reserved for issuance under the direct stock purchase feature of the Plan, 961,688 shares of our common stock remain available for sale.

We are a principal investment firm primarily focused on providing customized debt and equity financing to lower middle market (“LMM”) companies and debt capital to middle market (“Middle Market”) companies. We seek to achieve our investment objective through our LMM, Private Loan, and Middle Market investment strategies. Our LMM investment strategy involves investments in companies that generally have annual revenues between $10 million and $150 million and our LMM portfolio investments generally range in size from $5 million to $75 million. Our Middle Market investment strategy involves investments in companies that are generally larger in size than our LMM companies, with annual revenues typically between $150 million and $1.5 billion, and our Middle Market investments generally range in size from $3 million to $25 million. Our private loan (“Private Loan”) investment strategy involves

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investments in companies that are consistent with the size of the companies in our LMM and Middle Market investment strategies, and our Private Loan investments generally range in size from $10 million to $75 million.

The LMM, Private Loan and Middle Market securities in which we invest generally would be rated below investment grade if they were rated by rating agencies. Below investment grade securities, which are often referred to as “junk,” have predominantly speculative characteristics with respect to the issuer’s capacity to pay interest and repay principal. They may also be difficult to value and are illiquid.

We are an internally managed, closed end, non-diversified management investment company that has elected to be treated as a business development company (“BDC”) under the Investment Company Act of 1940, as amended. Our principal investment objective is to maximize our portfolio’s total return by generating current income from our debt investments and current income and capital appreciation from our equity and equity-related investments, including warrants, convertible securities and other rights to acquire equity securities in a portfolio company.

Our common stock is listed on the New York Stock Exchange (“NYSE”) under the symbol “MAIN.” On March 1, 2022, the last reported sale price of our common stock on the NYSE was $42.75 per share, and the net asset value per share of our common stock on December 31, 2021 (the last date prior to the date of this prospectus on which we determined our net asset value per share) was $25.29.

Investing in our common stock involves a high degree of risk, and should be considered highly speculative. You should carefully review the risks and uncertainties, including the risk of leverage and dilution, described in the section titled “Supplementary Risk Factors” beginning on page S-6 of this prospectus supplement, the section titled “Risk Factors” in our most recently filed Annual Report on Form 10-K, and under similar headings in the other documents that are filed on or after the date hereof and incorporated by reference into this prospectus supplement and the accompanying prospectus before investing in our common stock.

This prospectus supplement and the accompanying prospectus contain important information about us that a prospective investor should know before investing in our common stock. We may also authorize one or more free writing prospectuses to be provided to you in connection with this offering. You should carefully read this prospectus supplement, the accompanying prospectus, and any related free writing prospectus, and the documents incorporated by reference, before investing in our common stock. We file annual, quarterly and current reports, proxy statements and other information with the Securities and Exchange Commission, or SEC. This information is available free of charge by contacting us at 1300 Post Oak Boulevard, 8th Floor, Houston, Texas 77056 or by telephone at (713) 350-6000 or on our website at www.mainstcapital.com. Information contained on our website is not incorporated by reference into this prospectus supplement or the accompanying prospectus, and you should not consider that information to be part of this prospectus supplement or the accompanying prospectus. The SEC also maintains a website at www.sec.gov that contains such information.

Neither the Securities and Exchange Commission nor any state securities commission, nor any other regulatory body, has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus supplement is March 3, 2022

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Prospectus Supplement

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Prospectus

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ABOUT THIS DOCUMENT

This document is in two parts. The first part is this prospectus supplement, which describes the terms of this offering of common stock and also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference into the accompanying prospectus and this prospectus supplement. The second part is the accompanying prospectus, which provides more information about us and related matters. To the extent the information contained in this prospectus supplement differs from the information contained in the accompanying prospectus or any document filed prior to the date of this prospectus supplement and incorporated by reference, the information in this prospectus supplement shall control. Generally, when we refer to this “prospectus,” we are referring to both documents combined, together with any free writing prospectus that we have authorized for use in connection with this offering.

You should rely only on the information included or incorporated by reference in this prospectus supplement, the accompanying prospectus or in any free writing prospectus prepared by or on behalf of us that relates to this offering of common stock. We have not authorized any other person to provide you with different information or to make representations as to matters not stated in this prospectus supplement, the accompanying prospectus or in any free writing prospectus prepared by or on behalf of us that relates to this offering of common stock. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. If anyone provides you with different or inconsistent information, you should not rely on it. This prospectus supplement, the accompanying prospectus and any free writing prospectus prepared by or on behalf of us that relates to this offering of common stock do not constitute an offer to sell, or a solicitation of an offer to buy, any shares of our common stock by any person in any jurisdiction where it is unlawful for that person to make such an offer or solicitation or to any person in any jurisdiction to whom it is unlawful to make such an offer or solicitation. You should not assume that the information included in this prospectus supplement, the accompanying prospectus or in any such free writing prospectus is accurate as of any date other than their respective dates, or that any information incorporated by reference is accurate as of any date other than the date of the document incorporated by reference, regardless of the time of delivery of this prospectus supplement or of any of our securities.

Forward-Looking Statements

Information included or incorporated by reference in this prospectus supplement, the accompanying prospectus or in any free writing prospectus relating to this offering of common stock may contain forward-looking statements, which can be identified by the use of forward-looking terminology such as “may,” “will,” “expect,” “intend,” “anticipate,” “estimate,” or “continue” or the negative thereof or other variations thereon or comparable terminology. The matters described in the sections titled “Supplementary Risk Factors” in this prospectus supplement, “Risk Factors” in the accompanying prospectus and “Risk Factors” in our most recent Annual Report on Form 10-K, as well as in subsequent filings with the SEC, or in any free writing prospectus relating to this offering and certain other factors noted throughout or incorporated by reference in this prospectus supplement, the accompanying prospectus or in any free writing prospectus relating to this offering constitute cautionary statements identifying important factors with respect to any such forward-looking statements, including certain risks and uncertainties that could cause actual results to differ materially from those in such forward-looking statements. We undertake no obligation to revise or update any forward-looking statements but advise you to consult any additional disclosures that we may make directly to you or through reports that we may file in the future with the SEC, including annual reports on Form 10-K, quarterly reports on Form 10-Q and current reports on Form 8-K.

You should not place undue reliance on our forward-looking statements because the matters they describe are subject to known and unknown risks, uncertainties and other unpredictable factors, many of which are beyond our control. In addition to the information included or incorporated by reference in this prospectus supplement, please read carefully the sections titled “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” in our most recent Annual Report on Form 10-K and in other documents we may file with the SEC, as well as the section titled “Cautionary Statement Concerning Forward-Looking Statements” in the accompanying prospectus, before making an investment in our common stock.

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SUMMARY OF THE DIRECT STOCK PURCHASE FEATURE OF THE PLAN

The following summary highlights selected information about the direct stock purchase feature of the Plan, but may not contain all of the information that may be important to you. You should carefully read the detailed description of the direct stock purchase feature of the Plan contained in this prospectus supplement before you decide to participate in the direct stock purchase feature of the Plan.

Participation

Current Stockholders. If you currently own shares in the Company, you can participate in the direct stock purchase feature of the Plan by completing an authorization form and submitting it to American Stock Transfer & Trust Company LLC, the Plan Administrator. The initial investment for existing record holders is $100. Please see Question 6 under the section entitled “Terms and Conditions of the Direct Stock Purchase Feature of the Plan” for more detailed information.

New Investors. If you do not own any shares in the Company, you can participate in the direct stock purchase feature of the Plan by enrolling in the Plan and making an initial purchase of the Company’s shares through the direct stock purchase feature of the Plan with a minimum initial investment of at least $250 (or $100 if you sign up for automatic monthly investments), but not more than $25,000. Once you are a stockholder, the minimum purchase amount is reduced to $100. Please see Question 6 under the section entitled “Terms and Conditions of the Direct Stock Purchase Feature of the Plan” for more detailed information.

Advantages and Disadvantages

The primary advantages of the direct stock purchase feature of the Plan are as follows:

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The risks associated with participating in the direct stock purchase feature of the Plan are described under the heading “Supplementary Risk Factors” beginning on page S-6 of this prospectus supplement.

Source of Shares

The Plan Administrator will purchase shares directly from us as newly issued common stock, in the open market or in privately negotiated transactions with third parties. Please see Questions 10 and 12 under the section entitled “Terms and Conditions of the Direct Stock Purchase Feature of the Plan” for more detailed information.

Purchase Price

The purchase price for shares under the direct stock purchase feature of the Plan depends on whether the Plan Administrator obtains your shares by purchasing them directly from us, in the open market or in privately negotiated transactions with third parties:

Tracking Your Investments

As a participant in the direct stock purchase feature of the Plan, you will receive periodic statements showing the details of each transaction and the share balance in your Plan account. Please see Question 22 under the section entitled “Terms and Conditions of the Direct Stock Purchase Feature of the Plan” for more detailed information.

Plan Administrator

We have appointed American Stock Transfer & Trust Company LLC as the administrator of the Plan. Please see Question 2 under the section entitled “Terms and Conditions of the Direct Stock Purchase Feature of the Plan” for more detailed information.

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FEES AND EXPENSES

The following table is intended to assist you in understanding the costs and expenses that an investor in this offering will bear directly or indirectly. We caution you that some of the percentages indicated in the table below are estimates and may vary. Except where the context suggests otherwise, whenever this prospectus supplement contains a reference to fees or expenses paid by “you,” “us” or “Main Street,” or that “we” will pay fees or expenses, stockholders will indirectly bear such fees or expenses as investors in us.

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Example

The following example demonstrates the projected dollar amount of total cumulative expenses that would be incurred over various periods with respect to a hypothetical investment in our common stock. In calculating the following expense amounts, we have assumed we would have no additional leverage and that our annual operating expenses would remain at the levels set forth in the table above.

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The example and the expenses in the table above should not be considered a representation of our future expenses, and actual expenses may be greater or less than those shown. While the example assumes, as required by the SEC, a 5.0% annual return, our performance will vary and may result in a return greater or less than 5.0%. In addition, while the example assumes reinvestment of all dividends at net asset value, participants in the dividend reinvestment feature of our dividend reinvestment and direct stock purchase plan will receive a number of shares of our common stock, determined by dividing the total dollar amount of the dividend payable to a participant by (i) the market price per share of our common stock at the close of trading on a valuation date determined by our Board of Directors for each dividend in the event that we use newly issued shares to satisfy the share requirements of the dividend reinvestment plan or (ii) the average purchase price of all shares of common stock purchased by the Plan Administrator in the event that shares are purchased in the open market to satisfy the share requirements of the dividend reinvestment feature of the dividend reinvestment and direct stock purchase plan, which may be at, above or below net asset value. See “Dividend Reinvestment and Direct Stock Purchase Plan” in the accompanying prospectus for additional information regarding the dividend reinvestment feature of the Plan.

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SUPPLEMENTARY RISK FACTORS

Investing in our common stock, including through the direct stock purchase feature of the Plan, involves a high degree of risk. In addition to the other information contained or incorporated by reference in this prospectus supplement and the accompanying prospectus, you should carefully consider the following supplementary risk factors together with the risk factors and other information included or incorporated by reference in this prospectus supplement and the accompanying prospectus before making an investment. These risks are not the only risks we face. Additional risks and uncertainties not presently known to us or not presently deemed material by us might also impair our operations and performance. If any of these risks occur, our business, financial condition and results of operations could be materially and adversely affected. In such case, the market price of our common stock could decline, and you may lose part or all of your investment.

No interest will be paid on funds pending investment.

If you wish to make regular periodic purchases without writing checks, you can authorize automatic monthly withdrawals from your U.S. bank account. Participants’ bank accounts are debited on the 10th day of each month (or, if that day is not a business day, then on the prior business day) and funds will be invested beginning on the next applicable Cash Purchase Investment Date. Pending such investment, no interest is paid on optional cash investments held by the Plan Administrator. In addition, optional cash payments of less than the amounts required by the Plan and that portion of any optional cash payment which exceeds the maximum monthly purchase limit of $25,000, are subject to return to you without interest.

Participants will have no control over the purchase or sale price for shares acquired or disposed of through the Plan.

Participants have no control over the share price or the timing of the purchase or sale of Plan shares. Participants cannot designate a specific price or a specific date at which to purchase or sell shares of our common stock or the selection of a broker/dealer through or from whom purchases or sales are made. Participants will not know the exact number of shares purchased until after any particular Cash Purchase Investment Date. In addition, because the Plan Administrator must receive funds for a cash purchase prior to the actual Cash Purchase Investment Date of the common stock, your investments may be exposed to changes in market conditions.

No assurance of a profit or protection from losses on Shares purchased under the direct stock purchase feature of the Plan.

Other than as described above, the risks related to your investment in the direct stock purchase feature of the Plan is no different from any investment in shares of our common stock held by you. If you choose to participate in the direct stock purchase feature of the Plan, then you should recognize that none of us, our subsidiaries and affiliates, nor the Plan Administrator can assure you of a profit or protect you against loss on the shares that you purchase under the direct stock purchase feature of the Plan. You bear the risk of loss in value and enjoy the benefits of gains with respect to all of your shares.

USE OF PROCEEDS

We intend to initially use the net proceeds from this offering to repay outstanding debt borrowed under our revolving credit facility (the “Credit Facility”). However, through re-borrowing of the initial repayments under our Credit Facility, we intend to use the net proceeds from this offering (i) to make investments in accordance with our investment objective and strategies described in this prospectus supplement, the accompanying prospectus and any free writing prospectus relating to this offering, (ii) to make investments in marketable securities and idle funds investments, which may include investments in secured intermediate term bank debt, rated debt securities and other income producing investments, (iii) to pay our operating expenses and other cash obligations, and (iv) for general corporate purposes.

On March 1, 2022, we had approximately $248 million outstanding under our Credit Facility. Our Credit Facility matures in April 2026, unless extended, and bears interest, at our election, on a per annum basis at a rate equal to the applicable LIBOR rate plus (i) 1.875% (or the applicable base rate plus 0.875%), as long as we meet certain agreed upon excess collateral and maximum leverage requirements or (ii) 2.0% (or the applicable base rate plus 1.0%) otherwise. Amounts repaid under our Credit Facility will remain available for future borrowings.

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TERMS AND CONDITIONS OF THE DIRECT

STOCK PURCHASE FEATURE OF THE PLAN

The following are material terms and conditions of the direct stock purchase feature of the Plan.

PURPOSE

1.What is the purpose of the direct stock purchase feature of the Plan?

The primary purpose of the direct stock purchase feature of the Plan is to give holders of shares of our common stock and new investors a convenient and economical way to acquire additional shares of our common stock by making optional cash payments to purchase shares of our common stock. In this way, the direct stock purchase feature of the Plan is intended to benefit our long-term investors by allowing them to increase their investment in our common stock. The direct stock purchase feature of the Plan also provides us with a cost-efficient way to raise additional capital through the direct sale of our common stock to participants in the direct stock purchase feature of the Plan.

ADMINISTRATION

2.Who administers the Plan?

American Stock Transfer & Trust Company LLC has been appointed as administrator of the Plan. You should send all correspondence with the Plan Administrator to:

American Stock Transfer & Trust Company LLC

6201 15th Avenue

Brooklyn, NY 11219

All transaction processing should be directed to:

American Stock Transfer & Trust Company LLC

P.O. Box 922

Wall Street Station

New York, NY 10269-0560

Plan Administration Department

Please mention Main Street Capital Corporation and this Plan in all correspondence with the Plan Administrator. In addition, you may call the Plan Administrator at 1-866-706-8371 or contact the Plan Administrator via the internet at www.astfinancial.com.

The Company may replace the Plan Administrator at any time upon written notice to the Plan Administrator and may designate another qualified administrator as successor Plan Administrator for all or a part of the Plan Administrator’s functions under the Plan. All participants would be notified of any such change. If the Company changes the Plan Administrator, references in this prospectus to Plan Administrator shall be deemed to be references to the successor Plan Administrator, unless the context requires otherwise.

3.What are the responsibilities of the Plan Administrator?

The Plan Administrator’s responsibilities principally include:

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Holding Shares. If you purchase shares through optional cash payments and do not choose to have the dividends or distributions that are paid with respect to these shares reinvested, you must indicate that the shares are not to be enrolled in the dividend reinvestment feature of the Plan program. The Plan Administrator will hold any shares you choose to enroll in the dividend reinvestment feature of the Plan and will register them in the Plan Administrator’s name (or that of its nominee) as your agent.

Receipt of Dividends or Distributions. As record holder for the Plan shares, the Plan Administrator will receive dividends or distributions on all Plan shares held on the record date, will credit these dividends or distributions to your Plan account on the basis of whole or fractional Plan shares held in such account, and will automatically reinvest such dividends or distributions in additional common stock unless you select the cash payment only option on the authorization form or direct the Plan Administrator that you wish to receive cash payments only (which instructions can always be changed by providing notice to the Plan Administrator). Any remaining portion of cash dividends or distributions not designated for reinvestment will be sent to you. The record date associated with a particular dividend or distribution is referred to in this Plan as a “dividend record date.”

Other Responsibilities. The Plan Administrator also acts as dividend disbursing agent, transfer agent and registrar for our common stock.

Replacement Administrator. If the Plan Administrator resigns or otherwise ceases to act as Plan Administrator, we will appoint a new Plan Administrator to administer the Plan.

ELIGIBILITY AND ENROLLMENT

4.Who is eligible to participate in the direct stock purchase feature of the Plan?

Record Owners. You are a record owner if you own shares of our common stock that are registered in your name with our transfer agent. If you are a record owner, you may participate directly in any or all of the features of the direct stock purchase feature of the Plan.

Beneficial Owners. You are a beneficial owner if you own shares of our common stock that are registered in the name of a broker, bank or other nominee. If you are a beneficial owner, you must either (i) become a record owner by having one or more shares transferred into your own name, or (ii) coordinate your participation in the direct stock purchase feature of the Plan through the broker, bank or other nominee in whose name your common stock is held.

New Investors. If you do not currently own shares of our common stock, you can participate in the Plan by making an initial purchase of shares of our common stock through the direct stock purchase feature of the Plan with a minimum investment of $250 (or $100 if you sign up for automatic monthly investments).

Regulations in certain countries may limit or prohibit participation in this type of plan. Persons residing outside the United States who wish to participate in the direct stock purchase feature of the Plan should first determine whether they are subject to any governmental regulation prohibiting their participation.

You may not participate in the direct stock purchase feature of the Plan if it would be unlawful for you to do so in the jurisdiction where you are a citizen or, if you are a corporation or other entity, where you are organized or

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domiciled. If you are a citizen of, or organized or domiciled in, a country other than the U.S., you should independently confirm that by participating in the direct stock purchase feature of the Plan you will not violate local laws governing, among other matters, taxes, currency and exchange controls, stock registration and foreign investments. We reserve the right to terminate participation of any participant if we deem it advisable under any foreign laws or regulations.

The direct stock purchase feature of the Plan is designed for long-term investors who would like to invest and build ownership of shares of our common stock over time. The direct stock purchase feature of the Plan is not intended to provide stockholders with a mechanism for generating short-term profits through rapid turnover of shares acquired at a discount. Further, the direct stock purchase feature of the Plan’s intended purpose precludes any individual or entity from establishing a series of related accounts for the purpose of conducting arbitrage operations or exceeding the optional monthly cash investment limit. You should not use the direct stock purchase feature of the Plan to engage in short-term trading activities that could change the normal trading volume of shares of our common stock. If you engage in short-term trading activities, we may prevent you from participating in the direct stock purchase feature of the Plan. We reserve the right, in our sole discretion, to modify, deny, suspend or terminate participation by a Plan participant who, in our determination, is using the direct stock purchase feature of the Plan for purposes inconsistent with the intended purpose of the direct stock purchase feature of the Plan or which adversely affect the price of our common stock. In such an event, the Plan Administrator will notify the participant in writing of its action and will continue to hold the participant’s shares in book-entry form, but will no longer reinvest the participant’s dividends or distributions, or accept optional cash investments from the participant.

6.How do I become a participant in the direct stock purchase feature of the Plan?

Record Holders. Record holders may join the plan by completing and signing an authorization form and returning it to the Plan Administrator or by following the enrollment procedures specified on the Plan Administrator’s website at www.astfinancial.com. Authorization forms may be obtained at any time by written request, by telephoning the Plan Administrator at the address and telephone number provided in Question 2, or via the internet at the Plan Administrator’s website. The initial minimum investment for existing record holders is $100.

Beneficial Holders. A beneficial holder may request that the number of shares the beneficial holder wishes to be enrolled in the direct stock purchase feature of the Plan be re-registered by the broker, bank or other nominee in the beneficial holder’s own name as record owner in order to participate directly in the direct stock purchase feature of the Plan. Alternatively, beneficial holders who wish to join the direct stock purchase feature of the Plan may instruct their broker, bank or other nominee to arrange participation in the direct stock purchase feature of the Plan on the beneficial holder’s behalf. The broker, bank or other nominee should then make arrangements with its securities depository, and the securities depository will provide the Plan Administrator with the information necessary to allow the beneficial holder to participate in the direct stock purchase feature of the Plan.

New Investors. If you do not currently own any shares of our common stock, you may enroll in the direct stock purchase feature of the Plan by making an initial purchase of shares of our common stock through the direct stock purchase feature of the Plan with a minimum investment of $250 (or $100 if you sign up for automatic monthly investments), but your initial investment cannot exceed $25,000. The new investor should complete the portions of the authorization form for a new investor wishing to become a participant and should designate the amount of the initial investment in our common stock. At the same time, the new participant may designate all, some portion or none of the purchased shares to be enrolled in the dividend reinvestment program. The authorization form should be returned to the Plan Administrator, with payment, on or before the applicable dates described in Question 7. The new investors may also follow the enrollment procedures specified on the Plan Administrator’s website at www.astfinancial.com to join the direct stock purchase feature of the Plan. Online enrollment should be completed on or before the applicable dates described in Question 7. Once you are a stockholder, the minimum purchase amount is reduced to $100.

7.When will my participation in the direct stock purchase feature of the Plan begin?

If you have submitted your authorization form to make automatic monthly investments under the direct stock purchase feature of the Plan, the Plan Administrator must receive authorization two business days before the Cash Purchase Investment Date.

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In the case of new investors making an initial investment, both the authorization form and full payment of their designated initial investment must be received two business days before the Cash Purchase Investment Date.

Once you enroll in the direct stock purchase feature of the Plan, you will remain enrolled in the direct stock purchase feature of the Plan until you withdraw, we terminate your participation or we terminate the Plan.

8.What does the Plan Administrator’s website provide?

Instead of submitting an authorization form, you can participate in the direct stock purchase feature of the Plan by accessing the Plan Administrator’s website at www.astfinancial.com. The following services are available to you online:

OPTIONAL CASH INVESTMENTS

9.How do I make optional cash investments?

Once you have enrolled in the direct stock purchase feature of the Plan by submitting an authorization form, you may make optional cash investments at any time in three ways:

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Insufficient Funds. A $25 fee will be assessed if any check or deposit is returned unpaid or if an automatic withdrawal from your bank account fails due to insufficient funds. In addition, the Plan Administrator will consider null and void the request for any optional cash investment associated with insufficient funds and will immediately remove any shares already credited to your account in anticipation of receiving those funds. The foregoing fee and any other incidental costs associated with the insufficient funds will be collected by the Plan Administrator through the sale of an appropriate number of shares from your Plan account. If the net proceeds from the sale of those shares are insufficient to satisfy the balance of the uncollected amounts, the Plan Administrator may sell additional shares from your account as necessary to satisfy the uncollected balance.

No interest is paid on your payment pending its investment in shares of our common stock. During the period that an optional cash investment is pending, the collected funds in the possession of the Plan Administrator may be invested in money market mutual funds registered under the Investment Company Act of 1940 (including those of an affiliate of the Plan Administrator or for which the Plan Administrator or any of its affiliates provides management advisory or other services) consisting entirely of (i) direct obligations of the United States, or (ii) obligations fully guaranteed by the United States. The Plan Administrator will retain any investment income from such investments and will bear the risk of loss from such investments.

10.When will shares be purchased?

If the Plan Administrator acquires shares directly from us, then the date on which the Plan Administrator will make such cash investments, which we refer to as the “Cash Purchase Investment Date,” will be the 15th of each month (or the previous NYSE trading day if the 15th day is not an NYSE trading day). If the Plan Administrator acquires shares from parties other than us, it will attempt to buy shares of our common stock in the open market through a registered broker-dealer or privately negotiated transaction. Such purchases may begin before or after the Cash Purchase Investment Date, and will be completed no later than thirty (30) days following such date, except where completion at a later date is necessary or advisable under any applicable U.S. federal or state securities laws or regulations.

Optional cash investments are subject to a monthly minimum purchase requirement of $100 and a maximum purchase limit of $25,000. For purposes of the Plan, we may aggregate all dividend reinvestments and optional cash investments for participants with more than one account. We reserve the right to not honor requests for investments if we deem that an individual is using the Plan as a trading account. The Plan has been designed to offer individuals with the opportunity to build equity and not as trading account. In addition, all Plan accounts that we believe to be under common control or management or to have common ultimate beneficial ownership may be aggregated. Unless we have determined, in our sole discretion, that reinvestment of dividends and optional cash investments for each such account would be consistent with the purposes of the Plan, we have the right to aggregate all such accounts and to return, without interest, within 30 days of receipt, any amounts in excess of the investment limitations applicable to a single account received in respect of all such accounts.

COMMON STOCK USED TO SATISFY SHARE OBLIGATIONS

12.What is the source of shares to be purchased under the direct stock purchase feature of the Plan?

Either newly issued shares or shares purchased on the open market or in privately negotiated transactions with third parties, at our or the Plan Administrator’s discretion, will be used to satisfy any share obligations under the Plan (subject to the regulatory matter described in Question 14 below). Shares issued directly by us will consist of authorized

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but unissued shares of common stock. We may change the source of the common stock for the Plan, in our sole discretion, without providing you notice that we are doing so.

13.At what price will shares be issued or purchased?

We may, at our sole discretion, offer a discount of up to 5% of the market price, as calculated as set forth herein (exclusive of any applicable fees we may pay on your behalf), on issuances or purchases of common stock under the direct stock purchase feature of the Plan. We are not required to issue or sell shares at a discount under the direct stock purchase feature of the Plan or to pay a discount with respect to shares purchased by the Plan Administrator in the open market. If we implement discounts on any feature of the direct stock purchase feature of the Plan, any such discounts will be made at our sole discretion; and the discount rate we may offer will be subject to change or discontinuance at our discretion and without prior notice to participants in the direct stock purchase feature of the Plan. The discount rate, if any, will be determined by us from time to time based on a review of current market conditions, the level of participation in the direct stock purchase feature of the Plan, our current and projected capital needs and other factors that we deem to be relevant. Any discounts that we are offering under the Plan will be disclosed on the Plan Administrator’s website at www.astfinancial.com.

14.Are there any other limits on the purchase of shares of common stock under the Plan?

We are prohibited from selling shares of our common stock at a price that is, after deducting any selling commissions, less than the net asset value per share of our common stock at the time of the sale, except (i) with the requisite approval of our common stockholders or (ii) under such other circumstances as the SEC may permit. In addition, we cannot issue shares of our common stock below net asset value unless our Board of Directors determines that it would be in our and our stockholders’ best interests to do so. We did not seek stockholder authorization to issue common stock at a price below net asset value per share at our 2021 annual meeting of stockholders, and have not sought such stockholder authorization since 2012, because our common stock price per share has been trading significantly above the current net asset value per share of our common stock, but we may seek such authorization at future annual meetings or special meetings of stockholders.

Sales by us of our common stock at a discount from our net asset value pose potential risks for our existing stockholders whether or not they participate in the offering, as well as for new investors who participate in the offering. See “Sales of Common Stock Below Net Asset Value” in the accompanying prospectus.

STOCK CERTIFICATES AND SAFEKEEPING

15.Will I receive certificates for shares purchased through the direct stock purchase feature of the Plan?

Normally, common stock purchased for you under the direct stock purchase feature of the Plan will be held in the name of the Plan Administrator or its nominee. The Plan Administrator will credit the shares to your account for the

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direct stock purchase feature of the Plan in “book-entry” form. This service protects against loss, theft or destruction of certificates evidencing common stock.

16.Can I get certificates if I want them?

No certificates will be issued to you for shares in the Plan unless you submit a written request to the Plan Administrator or, in certain cases, until your participation in the direct stock purchase feature of the Plan is terminated. At any time, you may request the Plan Administrator to send a certificate for some or all of the whole shares credited to your account. This request should be mailed to the Plan Administrator at the address set forth in the answer to Question 2 or made via the internet on the Plan Administrator’s website at www.astfinancial.com. There is no fee for this service. Any remaining whole shares and any fractions of shares will remain credited to your Plan account. Certificates for fractional shares will not be issued under any circumstances.

17.May I deposit stock certificates I currently hold into my Plan account for safekeeping?

You may also elect to deposit with the Plan Administrator certificates for common stock that you own and that are registered in your name for safekeeping under the plan for a fee of $7.50 payable each time you deposit certificates with the Plan Administrator. The Plan Administrator will credit the common stock represented by the certificates to your account in “book-entry” form and will combine the shares with any whole and fractional shares then held in your Plan account. In addition to protecting against the loss, theft or destruction of your certificates, this service is convenient if and when you sell shares of common stock through the Plan. Because you bear the risk of loss in sending certificates to the Plan Administrator, you should send certificates by registered mail, return receipt requested, and properly insured to the address specified in Question 2 above.

18.In whose name will certificates be registered when issued?

Your Plan account will be maintained in the name in which your certificates were registered at the time of your enrollment in the direct stock purchase feature of the Plan. Stock certificates for those shares purchased under the direct stock purchase feature of the Plan will be similarly registered when issued upon your request. If your shares are held through a broker, bank or other nominee, such request must be placed through your broker, bank or other nominee.

SALE AND TRANSFER OF SHARES

19.How can I sell shares?

You may instruct the Plan Administrator to sell all or any part of the shares held in your Plan account by doing any of the following:

If there is more than one individual owner on the Plan account, all participants must authorize the transaction and sign the instruction. As with issuances and purchases, the Plan Administrator aggregates all requests to sell shares and then sells the total share amount on the open market through a broker. Sales will be made daily, unless the Plan Administrator, at its discretion, determines to sell shares less frequently (but not later than five trading days after receipt) if the total number of the shares to be sold is not sufficient.

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If you sell or transfer only a portion of the shares in your Plan account, you will remain a participant in the direct stock purchase feature of the Plan and may continue to make optional cash investments and reinvest dividends or distributions. The Plan Administrator will continue to reinvest the dividends or distributions on the shares credited to your account unless you notify the Plan Administrator that you wish to withdraw from the dividend reinvestment feature of the Plan.

The Plan requires you to pay all costs associated with the sale of your shares under the Plan. You will receive the proceeds of the sale, less a $15 service fee per transaction and a $0.10 per share commission paid to the Plan Administrator and less any other applicable fees by check. A Form 1099-B will be mailed to you in February of each year related to your sales of shares in the prior year for income tax purposes.

Termination of Account Upon Sale of All Shares. If the Plan Administrator sells all shares held in your Plan account, the Plan Administrator will automatically terminate your account. In this case, you will have to complete and file a new authorization form to rejoin the direct stock purchase feature of the Plan.

Timing and Control. Because the Plan Administrator will sell the shares on behalf of the Plan, neither we nor any participant in the Plan have the authority or power to control the timing or pricing of shares sold or the selection of the broker making the sales. Therefore, you will not be able to precisely time your sales through the Plan, and will bear the market risk associated with fluctuation in the price of our shares. That is, if you send in a request to sell shares, it is possible that the market price of our shares could go down or up before the broker sells your shares and the per share sales price you receive will be the average price of all shares sold for the Plan participants with respect to that sale date. In addition, you will not earn interest on a sales transaction.

Alternatively, you can transfer some or all of the shares held in your Plan account to your account with a broker or bank, who can then sell the shares for you. If you need additional assistance regarding the transfer of your shares, please telephone the Plan Administrator, and consult your broker or bank about the fees and expenses related to their sale of your shares.

The price of our common stock fluctuates on a daily basis. The price may rise or fall after you submit your request to sell and prior to the ultimate sale of your shares of our common stock. The price risk will be borne solely by you. You cannot revoke your request to sell once it is made. The Plan Administrator will report to both the IRS and the participant Cost Basis for shares purchased or sold.

TERMINATION OF PARTICIPATION

20.How do I terminate my participation in the direct stock purchase feature of the Plan?

You may discontinue your participation in the direct stock purchase feature of the Plan at any time by notifying the Plan Administrator in writing at its mailing address or via its internet address specified in the answer to Question 2. Upon termination of your Plan account, you will receive a certificate for the whole shares held for you under the Plan free of charge. A cash payment will be made for any fractional shares held in your account at the time of termination based on the current market value less any applicable sales fees. Alternatively, if you so direct, the Plan Administrator will sell all or part of the shares credited to your Plan account by using the transaction stub on the bottom of your statement and mailing it to the address listed in Question 2. You may also make this request via the Plan Administrator’s internet site at www.astfinancial.com.

FEES AND COMMISSIONS

21.What are the costs of participating in the direct stock purchase feature of the Plan?

You will not pay any trading fees, brokerage commissions or service fees on common stock purchased through the direct stock purchase feature of the Plan. We will pay all costs of administration of the Plan. You will, however, be responsible for any trading fees, brokerage commissions or service fees paid in connection with your sale of shares from

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the Plan. Please refer to the following tabular summary of Plan fees and commissions for more information regarding the current costs of participating in the direct stock purchase feature of the Plan:

Summary of Fees and Commissions

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The Plan Administrator will deduct the applicable fees or commissions from the proceeds of the sale.

We and the Plan Administrator reserve the right to amend or modify this Plan Service Fee schedule at any time and from time to time.

REPORTS AND NOTICES TO PARTICIPANTS

22.How will I keep track of my investments?

The Plan Administrator will mail Plan statements after each investment. In addition, a notice will be mailed to you after each issue or purchase, which will include the number of shares issued or purchased and the issue or purchase price. You may also view your transaction history online by logging into your account. Details available online include stock price and transaction type and date.

You should retain these statements to determine the tax cost basis of the shares purchased for your account under the Plan. In addition, you will receive copies of other communications sent to our stockholders, including our annual report to stockholders, the notice of annual meeting and proxy statement in connection with our annual meeting of stockholders and Internal Revenue Service information for reporting dividends paid.

You can also view your account history and balance online by accessing the Plan Administrator’s website at www.astfinancial.com.

23.Where will notices be sent?

The Plan Administrator will address all of its notices to you at your last known address. You should notify the Plan Administrator promptly, in writing, of any change of address.

FEDERAL TAX CONSEQUENCES

A summary of the U.S. federal income tax consequences of holding shares of our common stock is set forth in the section titled “Certain U.S. Federal Income Tax Considerations” in the accompanying prospectus. We advise you to consult your own tax advisors to determine the tax consequences particular to your situation, including any applicable

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state, local or foreign income and other tax consequences that may result from your participation in the direct stock purchase feature of the Plan and your subsequent sale of shares of common stock acquired pursuant to the direct stock purchase feature of the Plan.

A summary of the effects of the U.S. federal income tax withholding provisions applicable to U.S. stockholders is set forth in the section titled “Certain U.S. Federal Income Tax Considerations” in the accompanying prospectus.

OTHER INFORMATION

26.How can I vote my shares?

You will receive proxy material for all shares in your Plan account. You may vote your shares of common stock either by designating the vote of the shares by proxy or by voting the shares in person at the meeting of stockholders. The proxy will be voted in accordance with your direction. If you do not provide voting instructions but timely and properly submit your proxy, all of your shares will be voted in accordance with the recommendations of the board of directors. If you do not return the proxy card or if you return it unsigned, none of your shares will be voted unless you vote in person at the meeting of stockholders.

Your entitlement in a rights offering related to the common stock will be based upon the number of whole shares credited to your Plan account. In the event of a rights offering, transaction processing may be curtailed or suspended by the Plan Administrator for a short period of time following the dividend record date for such action to permit the Plan Administrator to calculate the rights allocable to each account.

Transaction processing may be curtailed or suspended until the completion of any rights offering.

28.What happens if we declare a dividend payable in stock or declare a stock split?

Stock Dividends and Stock Splits. If dividends or distributions are paid in the form of shares of our common stock, or if shares of our common stock are distributed in connection with any stock split or similar transaction, each account balance will be adjusted to reflect the receipt of shares of our common stock paid or distributed. You will receive a statement indicating the number of shares or amount of cash dividends or distributions paid as a result of the transaction. Transaction processing may either be curtailed or suspended until the completion of any stock dividend, stock split or corporate action.

Other Capitalization Changes. If there occurs any other transaction that results in the number of outstanding shares of our common stock being increased or decreased, such as a recapitalization, reclassification, reverse stock split or other combination of shares of our common stock, or other increase or decrease in shares of our common stock effectuated without receipt of consideration by us, each account balance will be adjusted to reflect the results of such transaction. You will receive a statement indicating the effects of such transaction on your account balance.

29.Can the Plan be amended, modified, suspended or terminated?

We reserve the right to amend, modify, suspend or terminate the Plan at any time in our sole discretion. You will receive written notice of any material amendment, modification, suspension or termination. We and the Plan Administrator also reserve the right to change any administrative procedures of the Plan in our discretion.

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If we terminate the Plan, you will receive a certificate for all whole shares of common stock held in your Plan account and a check representing the value of any fractional shares based on the then-current market price. We also will return to you any uninvested dividends or distributions or optional cash payments held in your Plan account.

We reserve the right to terminate American Stock Transfer & Trust Company LLC as Plan Administrator and appoint another institution to serve as Plan Administrator, or to administer the Plan ourselves. All participants will receive notice of any such change, which may be by e-mail to participants electing to receive communications electronically of any such change.

30.Are there any risks associated with the Plan?

See “Supplementary Risk Factors” elsewhere in this prospectus supplement. Otherwise, your investment through the direct stock purchase feature of the Plan is no different from any investment in shares of our common stock held by you. If you choose to participate in the direct stock purchase feature of the Plan, then you should recognize that none of us, our subsidiaries and affiliates, nor the Plan Administrator can assure you of a profit or protect you against loss on the shares that you purchase under the direct stock purchase feature of the Plan. You bear the risk of loss in value and enjoy the benefits of gains with respect to all of your shares. You need to make your own independent investment and participation decisions consistent with your situation and needs. None of us, our subsidiaries and affiliates, nor the Plan Administrator can guarantee liquidity in the markets, and the value and marketability of your shares may be adversely affected by market conditions. For more information regarding risks relating to an investment in shares of our common stock, see “Supplementary Risk Factors” beginning on page S-6 of this prospectus supplement, “Risk Factors” in the accompanying prospectus and “Risk Factors” in our most recent Annual Report on Form 10-K and under similar headings in the other documents filed by us with the SEC on or after the date hereof and incorporated by reference into this prospectus supplement and the accompanying prospectus.

Plan accounts are not insured or protected by the Securities Investor Protection Corporation or any other entity and are not guaranteed by the FDIC or any government agency.

Neither we, our subsidiaries, our affiliates, nor the Plan Administrator will be liable for any act, or for any failure to act, as long as we or they have made good faith efforts to carry out the terms of the Plan, as described in this prospectus supplement and the accompanying prospectus and on the forms that are designed to accompany each investment or activity.

In addition, the purchase price for shares acquired through the direct stock purchase feature of the Plan will vary and cannot be predicted. The purchase price may be different from (more or less than) the price of acquiring shares on the open market on the relevant date. Your investment in direct stock purchase feature of the Plan shares will be exposed to changes in market conditions and changes in the market value of the shares. Your ability to sell—both as to timing and pricing terms and related expenses—or otherwise liquidate shares under the Plan is subject to the terms of the Plan and the withdrawal procedures. Also, no interest will be paid on dividends, distributions, cash or other funds held by the Plan Administrator pending investment or sale.

31.What are the responsibilities of Main Street and the Plan Administrator?

Neither we, our subsidiaries, our affiliates, nor the Plan Administrator will be liable for any act, or for any failure to act, as long as we or they have made good faith efforts to carry out the terms of the direct stock purchase feature of the Plan, as described in this prospectus and on the forms that are designed to accompany each investment or activity. This limitation of liability includes, but is not limited to, any claims of liability for:

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We, any of our agents and the Plan Administrator, will not have any duties, responsibilities or liabilities other than those expressly set forth in the Plan or as imposed by applicable laws, including U.S. federal and state securities laws. Since the Plan Administrator has assumed all responsibility for administering the Plan, we specifically disclaim any responsibility for any of the Plan Administrator’s actions or inactions in connection with the administration of the Plan. None of our directors, officers, employees or stockholders will have any personal liability under the Plan.

We, any of our agents and the Plan Administrator, will be entitled to rely on completed forms and the proof of due authority to participate in the direct stock purchase feature of the Plan, without further responsibility of investigation or inquiry.

32.How will you interpret and regulate the Plan?

Our officers are authorized to take any actions that are consistent with the Plan’s terms and conditions. We reserve the right to interpret and regulate the Plan as we deem necessary and desirable in connection with the Plan’s operations. Any such determination by us will be conclusive and binding on Plan participants.

33.What law governs the Plan?

The laws of the State of New York govern the Plan.

LEGAL MATTERS

Certain legal matters regarding the shares of common stock offered hereby will be passed upon for us by Dechert LLP, Washington D.C.

INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

The consolidated financial statements, financial highlights and Schedule 12-14 of Main Street Capital Corporation appearing in our Annual Report on Form 10-K for the year ended December 31, 2021 have been audited by Grant Thornton LLP, an independent registered public accounting firm, and incorporated in this prospectus supplement by reference. Such consolidated financial statements are incorporated by reference in reliance on the report of Grant Thornton LLP given on their authority as experts in accounting and auditing. The senior securities table of Main Street Capital Corporation, incorporated by reference into the accompanying prospectus and elsewhere in the registration statement, has been so included in reliance upon the report of Grant Thornton LLP, an independent registered public accounting firm.

Grant Thornton LLP’s principal business address is Grant Thornton Tower, 171 North Clark, Suite 200, Chicago, Illinois, 60601.

AVAILABLE INFORMATION

This prospectus supplement and the accompanying prospectus constitute part of a universal shelf registration statement on Form N-2 that we have filed with the SEC, together with any and all amendments and related exhibits, under the Securities Act. The registration statement contains additional information about us and our shares of common stock being offered by this prospectus supplement. Statements contained herein concerning any document filed as an exhibit are not necessarily complete, and, in each instance, reference is made to the copy of such document filed as an exhibit to the registration statement. Each such statement is qualified in its entirety by such reference.

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We file with or submit to the SEC annual, quarterly and current reports, proxy statements and other information meeting the informational requirements of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). The SEC maintains an Internet site that contains reports, proxy and information statements and other information filed electronically by us with the SEC, which are available free of charge on the SEC’s website at www.sec.gov. This information is also available free of charge by contacting us at 1300 Post Oak Boulevard, 8th Floor, Houston, Texas 77056 or by telephone at (713) 350-6000 or on our website at www.mainstcapital.com. Information contained on our website is not incorporated by reference into this prospectus supplement or the accompanying prospectus, and you should not consider that information to be part of this prospectus supplement or the accompanying prospectus.

INCORPORATION BY REFERENCE

We incorporate by reference in this prospectus supplement the documents listed below and any reports and other documents we file with the SEC pursuant to Sections 13(a), 13(c), 14, or 15(d) of the Exchange Act after the date of this prospectus supplement and prior to the termination of this offering (such reports and other documents deemed to be incorporated by reference into this prospectus supplement and to be part hereof from the date of filing of such reports and other documents); provided, however, that any document, report, exhibit (or portion of any of the foregoing) or other information “furnished” to the SEC pursuant to the Exchange Act shall not be incorporated by reference into this prospectus supplement:

Any statement contained in any document incorporated or deemed to be incorporated by reference herein shall be deemed to be modified or superseded for purposes of this prospectus supplement and the accompanying prospectus to the extent that a statement contained in this prospectus supplement or in any other subsequently filed document which also is or is deemed to be incorporated by reference in this prospectus supplement modifies or supersedes such earlier statement. Any statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this prospectus supplement.

We will provide without charge to each person, including any beneficial owner, to whom a copy of this prospectus supplement is delivered, upon written or oral request of any such person, a copy of any or all of the information that has been incorporated by reference in this prospectus supplement but not delivered with this prospectus supplement, excluding exhibits to a document unless an exhibit has been specifically incorporated by reference in that document. To obtain copies of these filings, see “Available Information” in this prospectus supplement.

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PROSPECTUS

Common Stock

Preferred Stock

Subscription Rights

Debt Securities

Main Street Capital Corporation is a principal investment firm primarily focused on providing customized debt and equity financing to lower middle market (“LMM”) companies and debt capital through our private loan and middle market investment strategies. Our LMM investment strategy involves investments in companies that generally have annual revenues between $10 million and $150 million and our LMM portfolio investments generally range in size from $5 million to $75 million. Our Middle Market investment strategy involves investments in companies that are generally larger in size than our LMM companies, with annual revenues typically between $150 million and $1.5 billion, and our Middle Market investments generally range in size from $3 million to $25 million. Our Private Loan investment strategy involves investments in companies that are consistent with the size of the companies in our LMM and Middle Market investment strategies, and our Private Loan investments generally range in size from $10 million to $75 million.

We are an internally managed, closed-end, non-diversified management investment company that has elected to be treated as a business development company (“BDC”) under the Investment Company Act of 1940, as amended. Our principal investment objective is to maximize our portfolio’s total return by generating current income from our debt investments and capital appreciation from our equity and equity related investments, including warrants, convertible securities and other rights to acquire equity securities in a portfolio company.

We may offer, from time to time in one or more offerings or series, our common stock, preferred stock, subscription rights or debt securities, which we refer to, collectively, as the “securities.” Our securities may be offered at prices and on terms to be disclosed in one or more supplements to this prospectus. In the event we offer common stock, the offering price per share of our common stock, less any underwriting commissions or discounts, will not be less than the net asset value per share of our common stock at the time of the offering, except (i) in connection with a rights offering to our existing stockholders, (ii) with the prior approval of the majority of our common stockholders or (iii) under such circumstances as the U.S. Securities and Exchange Commission (the “SEC”) may permit. Sales of common stock at prices below net asset value per share dilute the interests of existing stockholders, have the effect of reducing our net asset value per share and may reduce our market price per share.

Investing in our securities involves a high degree of risk and should be considered highly speculative. You should carefully review the risks and uncertainties, including the risk of leverage and dilution, described in the section titled “Risk Factors” included in or incorporated by reference into this prospectus, the applicable prospectus supplement and in any free writing prospectuses we have authorized for use in connection with a specific offering.

The LMM, Private Loan and Middle Market securities in which we invest generally would be rated below investment grade if they were rated by rating agencies. Below investment grade securities, which are often referred to as “junk,” have predominantly speculative characteristics with respect to the issuer’s capacity to pay interest and repay principal. They may also be difficult to value and are illiquid.

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Our common stock is listed on the New York Stock Exchange (“NYSE”) under the symbol “MAIN.” On March 1, 2022, the last reported sale price of our common stock on the NYSE was $42.75 per share, and the net asset value per share of our common stock on December 31, 2021 (the last date prior to the date of this prospectus on which we determined our net asset value per share) was $25.29.

This prospectus describes some of the general terms that may apply to an offering of our securities. We will provide the specific terms of these offerings and securities in one or more supplements to this prospectus. We may also authorize one or more free writing prospectuses to be provided to you in connection with these offerings. The prospectus supplement and any related free writing prospectus may also add, update, or change information contained in this prospectus. You should carefully read this prospectus, the applicable prospectus supplement, and any related free writing prospectus, and the documents incorporated by reference, before buying any of the securities being offered. We file annual, quarterly and current reports, proxy statements and other information with the SEC. This information is available free of charge by contacting us at 1300 Post Oak Boulevard, 8^th Floor, Houston, Texas 77056 or by telephone at (713) 350-6000 or on our website at www.mainstcapital.com. Information contained on our website is not incorporated by reference into this prospectus, and you should not consider that information to be part of this prospectus. The SEC also maintains a website at www.sec.gov that contains such information.

Neither the SEC nor any state securities commission, nor any other regulatory body, has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

This prospectus may not be used to consummate sales of securities unless accompanied by a prospectus supplement.

The date of this prospectus is March 3, 2022

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This prospectus is part of an automatic registration statement that we have filed with the Securities and Exchange Commission, or SEC, using the “shelf” registration process as a “well-known seasoned issuer” as defined in Rule 405 under the Securities Act of 1933, as amended (the “Securities Act”). Under this shelf registration statement, we may offer, from time to time in one or more offerings or series, our securities on terms to be determined at the time of the offering. This prospectus provides you with a general description of the securities that we may offer. Each time we use this prospectus to offer securities, we will provide a prospectus supplement that will contain specific information about the terms of that offering. We may also authorize one or more free writing prospectuses to be provided to you that may contain material information relating to these offerings. In a prospectus supplement or free writing prospectus, we may also add, update, or change any of the information contained in this prospectus or in the documents we have incorporated by reference into this prospectus. This prospectus, together with the applicable prospectus supplement, any related free writing prospectus, and the documents incorporated by reference into this prospectus and the applicable prospectus supplement, will include all material information relating to the applicable offering. Before buying any of the securities being offered, you should carefully read both this prospectus and the applicable prospectus supplement and any related free writing prospectus, together with the additional information described in the section titled “Available Information.”

This prospectus may contain estimates and information concerning our industry that are based on industry publications and reports. This information involves many assumptions and limitations, and you are cautioned not to give undue weight to these estimates. We have not independently verified the accuracy or completeness of the data contained

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in these industry publications and reports. The industry in which we operate is subject to a high degree of uncertainty and risk due to a variety of factors, including those described in the section titled “Risk Factors,” that could cause results to differ materially from those expressed in these publications and reports.

This prospectus includes summaries of certain provisions contained in some of the documents described in this prospectus, but reference is made to the actual documents for complete information. All of the summaries are qualified in their entirety by the actual documents. Copies of some of the documents referred to herein have been filed, will be filed, or will be incorporated by reference as exhibits to the registration statement of which this prospectus is a part, and you may obtain copies of those documents as described in the section titled “Available Information.”

You should rely only on the information included or incorporated by reference in this prospectus, any prospectus supplement or in any free writing prospectus prepared by or on behalf of us or to which we have referred you. We have not authorized any dealer, salesperson or other person to provide you with different information or to make representations as to matters not stated in this prospectus, any prospectus supplement or in any free writing prospectus prepared by or on behalf of us or to which we have referred you. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. If anyone provides you with different or inconsistent information, you should not rely on it. This prospectus, any applicable prospectus supplement and any free writing prospectus prepared by or on behalf of us or to which we have referred you do not constitute an offer to sell, or a solicitation of an offer to buy, any securities by any person in any jurisdiction where it is unlawful for that person to make such an offer or solicitation or to any person in any jurisdiction to whom it is unlawful to make such an offer or solicitation. You should not assume that the information included or incorporated by reference in this prospectus or any prospectus supplement or in any such free writing prospectus is accurate as of any date other than their respective dates.

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PROSPECTUS SUMMARY

This summary highlights information included elsewhere in this prospectus or incorporated by reference. It is not complete and may not contain all of the information that you should consider before making your investment decision. You should carefully read the entire prospectus, the applicable prospectus supplement, and any related free writing prospectus, including the risks of investing in our securities discussed in the section titled “Risk Factors” in the applicable prospectus supplement and any related free writing prospectus, and under similar headings in the other documents that are incorporated by reference into this prospectus. Before making your investment decision, you should also carefully read the information incorporated by reference into this prospectus, including our financial statements and related notes, and the exhibits to the registration statement of which this prospectus is a part. Any yield information contained or incorporated by reference in this prospectus related to debt investments in our investment portfolio is not intended to approximate a return on your investment in us and does not take into account other aspects of our business, including our operating and other expenses, or other costs incurred by you in connection with your investment in us.

Organization

Main Street Capital Corporation (“MSCC”) is a principal investment firm primarily focused on providing customized debt and equity financing to lower middle market (“LMM”) companies and debt capital to middle market (“Middle Market”) companies. The portfolio investments of MSCC and its consolidated subsidiaries are typically made to support management buyouts, recapitalizations, growth financings, refinancings and acquisitions of companies that operate in a variety of industry sectors. MSCC seeks to partner with entrepreneurs, business owners and management teams and generally provides “one stop” financing alternatives within its LMM portfolio. MSCC and its consolidated subsidiaries invest primarily in secured debt investments, equity investments, warrants and other securities of LMM companies based in the United States and in secured debt investments of Middle Market companies generally headquartered in the United States.

MSCC was formed in March 2007 to operate as an internally managed business development company (“BDC”) under the Investment Company Act of 1940, as amended (the “1940 Act”). MSCC wholly owns several investment funds, including Main Street Mezzanine Fund, LP (“MSMF”) and Main Street Capital III, LP (“MSC III” and, together with MSMF, the “Funds”), and each of their general partners. The Funds are each licensed as a Small Business Investment Company (“SBIC”) by the United States Small Business Administration (“SBA”). Because MSCC is internally managed, all of the executive officers and other employees are employed by MSCC. Therefore, MSCC does not pay any external investment advisory fees, but instead directly incurs the operating costs associated with employing investment and portfolio management professionals.

MSC Adviser I, LLC (the “External Investment Manager”) was formed in November 2013 as a wholly owned subsidiary of MSCC to provide investment management and other services to parties other than MSCC and its subsidiaries or their portfolio companies (“External Parties”) and receives fee income for such services. MSCC has been granted no-action relief by the SEC to allow the External Investment Manager to register as a registered investment adviser under the Investment Advisers Act of 1940, as amended (the “Advisers Act”). Since the External Investment Manager conducts all of its investment management activities for External Parties, it is accounted for as a portfolio investment of MSCC and is not included as a consolidated subsidiary of MSCC in MSCC’s consolidated financial statements.

MSCC has elected to be treated for U.S. federal income tax purposes as a regulated investment company (“RIC”) under Subchapter M of the Internal Revenue Code of 1986, as amended (the “Code”). As a result, MSCC generally will not pay corporate-level U.S. federal income taxes on any net ordinary taxable income or capital gains that it distributes to its stockholders.

MSCC has certain direct and indirect wholly owned subsidiaries that have elected to be taxable entities (the “Taxable Subsidiaries”). The primary purpose of the Taxable Subsidiaries is to permit MSCC to hold equity investments in portfolio companies which are “pass-through” entities for tax purposes.

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Unless otherwise noted or the context otherwise indicates, the terms “we,” “us,” “our,” the “Company” and “Main Street” refer to MSCC and its consolidated subsidiaries, which include the Funds and the Taxable Subsidiaries.

Overview

Our principal investment objective is to maximize our portfolio’s total return by generating current income from our debt investments and current income and capital appreciation from our equity and equity-related investments, including warrants, convertible securities and other rights to acquire equity securities in a portfolio company. We seek to achieve our investment objective through our LMM, Private Loan, and Middle Market investment strategies.

Our LMM investment strategy involves investments in companies that generally have annual revenues between $10 million and $150 million and our LMM portfolio investments generally range in size from $5 million to $75 million. Our Middle Market investment strategy involves investments in companies that are generally larger in size than our LMM companies, with annual revenues typically between $150 million and $1.5 billion, and our Middle Market investments generally range in size from $3 million to $25 million. Our private loan (“Private Loan”) investment strategy involves investments in companies that are consistent with the size of the companies in our LMM and Middle Market investment strategies, and our Private Loan investments generally range in size from $10 million to $75 million.

We seek to fill the financing gap for LMM businesses, which, historically, have had limited access to financing from commercial banks and other traditional sources. The underserved nature of the LMM creates the opportunity for us to meet the financing needs of LMM companies while also negotiating favorable transaction terms and equity participations. Our ability to invest across a company’s capital structure, from secured loans to equity securities, allows us to offer portfolio companies a comprehensive suite of financing options, or a “one stop” financing solution. Providing customized, “one stop” financing solutions is important to LMM portfolio companies. We generally seek to partner directly with entrepreneurs, management teams and business owners in making our investments. Our LMM portfolio debt investments are generally secured by a first lien on the assets of the portfolio company and typically have a term of between five and seven years from the original investment date.

Private Loan investments consist generally of loans that have been originated directly by us or through strategic relationships with other investment funds on a collaborative basis and are often referred to in the debt markets as “club deals.” Private Loan investments are typically similar in size, structure, terms and conditions to investments we hold in our LMM portfolio and Middle Market portfolio. Our Private Loan portfolio debt investments are generally secured by a first priority lien on the assets of the portfolio company and typically have a term of between three and seven years from the original investment date.

Our Middle Market portfolio investments primarily consist of direct investments in or secondary purchases of interest-bearing syndicated loans or debt securities in privately held companies based in the United States that are generally larger in size than the companies included in our LMM portfolio. Our Middle Market portfolio debt investments are generally secured by a first priority lien on the assets of the portfolio company and typically have an expected duration of between three and seven years from the original investment date.

Our other portfolio (“Other Portfolio”) investments primarily consist of investments that are not consistent with the typical profiles for our LMM, Private Loan or Middle Market portfolio investments, including investments which may be managed by third parties. In our Other Portfolio, we may incur indirect fees and expenses in connection with investments managed by third parties, such as investments in other investment companies or private funds.

Subject to changes in our cash and overall liquidity, our investment portfolio may also include short-term portfolio investments that are atypical of our LMM, Middle Market and Private Loan portfolio investments in that they are intended to be a short-term deployment of capital. These assets are typically expected to be liquidated in one year or less and are not expected to be a significant portion of the overall investment portfolio.

Our external asset management business is conducted through the External Investment Manager. The External Investment Manager earns management fees based on the assets of the funds under management and may earn incentive fees, or a carried interest, based on the performance of the funds managed.

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Our portfolio investments are generally made through MSCC, the Taxable Subsidiaries and the Funds. MSCC, the Taxable Subsidiaries and the Funds share the same investment strategies and criteria, although they are subject to different regulatory regimes (see “Business—Regulation” in our most recently filed Annual Report on Form 10-K, as well as in subsequent filings with the SEC, incorporated by reference herein). An investor’s return in MSCC will depend, in part, on the Taxable Subsidiaries’ and the Funds’ investment returns as they are wholly owned subsidiaries of MSCC.

The level of new portfolio investment activity will fluctuate from period to period based upon our view of the current economic fundamentals, our ability to identify new investment opportunities that meet our investment criteria, and our ability to consummate the identified opportunities. The level of new investment activity, and associated interest and fee income, will directly impact future investment income. In addition, the level of dividends paid by portfolio companies and the portion of our portfolio debt investments on non-accrual status will directly impact future investment income. While we intend to grow our portfolio and our investment income over the long term, our growth and our operating results may be more limited during depressed economic periods. However, we intend to appropriately manage our cost structure and liquidity position based on applicable economic conditions and our investment outlook. The level of realized gains or losses and unrealized appreciation or depreciation on our investments will also fluctuate depending upon portfolio activity, economic conditions and the performance of our individual portfolio companies. The changes in realized gains and losses and unrealized appreciation or depreciation could have a material impact on our operating results.

Because we are internally managed, we do not pay any external investment advisory fees, but instead directly incur the operating costs associated with employing investment and portfolio management professionals. We believe that our internally managed structure provides us with a better alignment of interests between our management team and our employees and our shareholders and a beneficial operating expense structure when compared to other publicly traded and privately held investment firms which are externally managed, and our internally managed structure allows us the opportunity to leverage our non-interest operating expenses as we grow our investment portfolio.

Through the External Investment Manager, we serve as the sole investment adviser and administrator to MSC Income pursuant to an Investment Advisory and Administrative Services Agreement entered into between the External Investment Manager and MSC Income (the “Advisory Agreement”). Under the Advisory Agreement, the External Investment Manager earns a 1.75% annual base management fee and a 20% incentive fee on MSC Income’s pre-investment fee net investment income above a specified hurdle rate, as well as an incentive fee on capital gains, in exchange for providing advisory services to MSC Income.

Additionally, the External Investment Manager has entered into an Investment Management Agreement with MS Private Loan Fund I, LP, a private investment fund with a strategy to co-invest with Main Street in Private Loan portfolio investments (the “Private Loan Fund”), pursuant to which the External Investment Manager provides investment advisory and management services to the Private Loan Fund in exchange for an asset-based fee and certain incentive fees.

We have entered into an agreement with the External Investment Manager to share employees in connection with its asset management business generally, and specifically for its relationship with MSC Income and its other clients. Through this agreement, we share employees with the External Investment Manager, including their related infrastructure, business relationships, management expertise and capital raising capabilities, and we allocate the related expenses to the External Investment Manager pursuant to the sharing agreement.

We have received an exemptive order from the SEC permitting co-investments among us, MSC Income and other funds and clients advised by the External Investment Manager in certain negotiated transactions where co-investing would otherwise be prohibited under the 1940 Act. We have made co-investments with, and in the future intend to continue to make co-investments with MSC Income, the Private Loan Fund and other clients advised by the External Investment Manager, in accordance with the conditions of the order. The order requires, among other things, that we and the External Investment Manager consider whether each such investment opportunity is appropriate for us and the External Investment Manager’s advised clients, as applicable, and if it is appropriate, to propose an allocation of the investment opportunity between such parties. Because the External Investment Manager may receive performance-

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based fee compensation from funds and clients advised by the External Investment Manager, this may provide the Company and the External Investment Manager an incentive to allocate opportunities to other participating funds and clients instead of us. However, both we and the External Investment Manager have policies and procedures in place to manage this conflict, including oversight by the independent members of our Board of Directors.

You should be aware that investments in our portfolio companies carry a number of risks including, but not limited to, investing in companies which may have limited operating histories and financial resources and other risks common to investing in below investment grade debt and equity investments in private, smaller companies. Please see “Risk Factors—Risks Related to Our Investments” in our most recently filed Annual Report on Form 10-K, as well as in subsequent filings with the SEC, for a more complete discussion of the risks involved with investing in our portfolio companies.

Our principal executive offices are located at 1300 Post Oak Boulevard, 8^th Floor, Houston, Texas 77056, and our telephone number is (713) 350-6000. We maintain a website at http://www.mainstcapital.com. Information contained on our website is not incorporated by reference into this prospectus, and you should not consider that information to be part of this prospectus.

Risks Associated with Our Business

Our business is subject to numerous risks, as described in the section titled “Risk Factors” in the applicable prospectus supplement and in any free writing prospectuses we have authorized for use in connection with a specific offering, and under similar headings in the documents that are incorporated by reference into this prospectus, including the section titled “Risk Factors” included in our most recent Annual Report on Form 10-K, as well as in subsequent filings with the SEC.

Dividend Reinvestment and Direct Stock Purchase Plan

We have adopted a dividend reinvestment and direct stock purchase plan (the “Plan”). The Plan primarily consists of a dividend reinvestment feature and a direct stock purchase feature. The direct stock purchase feature of the Plan is designed to provide new investors and existing holders of our common stock with a convenient and economical method to purchase shares of our common stock and is described in more detail in a separate prospectus supplement. The dividend reinvestment feature of the Plan, or the dividend reinvestment plan, provides for the reinvestment of dividends on behalf of our registered stockholders who hold their shares with American Stock Transfer & Trust Company, LLC, the plan administrator and our transfer agent and registrar, or certain brokerage firms that have elected to participate in our dividend reinvestment plan, unless a stockholder has elected to receive dividends in cash. For more information, see “Dividend Reinvestment and Direct Stock Purchase Plan.”

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The Offering

We may offer, from time to time in one or more offerings or series, our securities under this prospectus, together with the applicable prospectus supplement and any related free writing prospectus, at prices and on terms to be determined at the time of any offering. This prospectus provides you with a general description of the securities we may offer. Each time we offer a type or series of securities under this prospectus, we will provide a prospectus supplement that will describe the specific amounts, prices, and other important terms of the securities. The applicable prospectus supplement and any related free writing prospectus that we may authorize to be provided to you may also add, update, or change information contained in this prospectus or in documents we have incorporated by reference.

Our securities may be offered directly to one or more purchasers by us or through agents designated from time to time by us, or to or through underwriters or dealers. The prospectus supplement relating to the offering will disclose the terms of the offering, including the name or names of any agents or underwriters involved in the sale of our securities by us, the purchase price, and any fee, commission or discount arrangement between us and our agents or underwriters or among our underwriters or the basis upon which such amount may be calculated. See “Plan of Distribution.”

Set forth below is additional information regarding the offering of our securities:

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FEES AND EXPENSES

The following table is intended to assist you in understanding the costs and expenses that an investor in this offering will bear directly or indirectly. We caution you that some of the percentages indicated in the table below are estimates and may vary. Except where the context suggests otherwise, whenever this prospectus contains a reference to fees or expenses paid by “you,” “us” or “Main Street,” or that “we” will pay fees or expenses, stockholders will indirectly bear such fees or expenses as investors in us.

Example

The following example demonstrates the projected dollar amount of total cumulative expenses that would be incurred over various periods with respect to a hypothetical investment in our common stock. In calculating the

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following expense amounts, we have assumed we would have no additional leverage and that our annual operating expenses would remain at the levels set forth in the table above. In the event that shares to which this prospectus relates are sold to or through underwriters, a corresponding prospectus supplement will restate this example to reflect the applicable sales load.

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The example and the expenses in the table above should not be considered a representation of our future expenses, and actual expenses may be greater or less than those shown. While the example assumes, as required by the SEC, a 5.0% annual return, our performance will vary and may result in a return greater or less than 5.0%. In addition, while the example assumes reinvestment of all dividends at net asset value, participants in our dividend reinvestment plan will receive a number of shares of our common stock, determined by dividing the total dollar amount of the dividend payable to a participant by (i) the market price per share of our common stock at the close of trading on a valuation date determined by our Board of Directors for each dividend in the event that we use newly issued shares to satisfy the share requirements of the dividend reinvestment plan or (ii) the average purchase price of all shares of common stock purchased by the plan administrator in the event that shares are purchased in the open market to satisfy the share requirements of the dividend reinvestment plan, which may be at, above or below net asset value. See “Dividend Reinvestment and Direct Stock Purchase Plan” for additional information regarding our dividend reinvestment plan.

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FINANCIAL HIGHLIGHTS

The financial data as of and for each of the ten years ended December 31, 2021 is set forth in “Note F – Financial Highlights” in the notes to our audited consolidated financial statements included in our Annual Report on Form 10-K for the fiscal year ended December 31, 2021 and incorporated by reference into this prospectus in its entirety. The financial data has been audited by Grant Thornton LLP, an independent registered public accounting firm whose reports thereon are incorporated by reference in this prospectus. A copy of our Annual Report on Form 10-K filed with the SEC may be obtained from www.sec.gov or upon request. You should read these financial highlights in conjunction with our consolidated financial statements and notes thereto and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” incorporated by reference into this prospectus, any documents incorporated by reference in this prospectus or the accompanying prospectus supplement, or our Annual Reports on Form 10-K filed with the SEC.

RISK FACTORS

Investing in our securities involves a high degree of risk. Before deciding whether to invest in our securities, you should carefully consider the risks and uncertainties described in the section titled “Risk Factors” in the applicable prospectus supplement and any related free writing prospectus, and discussed in the section titled “Risk Factors” in our most recent Annual Report on Form 10-K, as well as in subsequent filings with the SEC, which are incorporated by reference into this prospectus in their entirety, together with other information in this prospectus, the documents incorporated by reference, and any free writing prospectus that we may authorize for use in connection with this offering. The risks described in these documents are not the only ones we face. Additional risks and uncertainties that we are unaware of, or that we currently believe are not material, may also become important factors that adversely affect our business. Past financial performance may not be a reliable indicator of future performance, and historical trends should not be used to anticipate results or trends in future periods. If any of these risks actually occurs, our business, reputation, financial condition, results of operations, revenue, and future prospects could be seriously harmed. This could cause our net asset value and the trading price of our securities to decline, resulting in a loss of all or part of your investment. Please also read carefully the section titled “Cautionary Statement Concerning Forward-Looking Statements.”

CAUTIONARY STATEMENT CONCERNING FORWARD-LOOKING STATEMENTS

This prospectus, including the documents that we incorporate by reference herein, contains, and any applicable prospectus supplement or free writing prospectus, including the documents we incorporate by reference therein, may contain forward-looking statements, including statements regarding our future financial condition, business strategy, and plans and objectives of management for future operations. All statements other than statements of historical facts, including statements regarding our future results of operations or financial condition, business strategy and plans, and objectives of management for future operations, are forward-looking statements. The forward-looking statements contained or incorporated by reference in this prospectus and any applicable prospectus supplement or free writing prospectus may include statements as to:

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In some cases, you can identify forward-looking statements because they contain words such as “anticipate,” “believe,” “contemplate,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “plan,” “potential,” “predict,” “project,” “should,” “target,” “will,” or “would” or the negative of these words or other similar terms or expressions, although not all forward-looking statements include these words or expressions. The forward-looking statements contained or incorporated by reference in this prospectus and any applicable prospectus supplement or free writing prospectus involve risks and uncertainties. Our actual results could differ materially from those implied or expressed in the forward-looking statements for any reason, including the factors set forth in “Risk Factors” in our most recent Annual Report on Form 10-K, as well as in subsequent filings with the SEC, and elsewhere contained or incorporated by reference in this prospectus and any applicable prospectus supplement or free writing prospectus. Other factors that could cause actual results to differ materially include:

Discussions containing these forward-looking statements may be found in the sections titled “Business,” “Risk Factors,” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” incorporated by reference from our most recent Annual Report on Form 10-K, as well as in subsequent filings with the SEC. We discuss in greater detail, and incorporate by reference into this prospectus in their entirety, many of these risks and uncertainties in the sections titled “Risk Factors” in the applicable prospectus supplement, in any free writing prospectus we may authorize for use in connection with a specific offering, and in our most recent Annual Report on Form 10-K, as well as in subsequent filings with the SEC. In addition, statements that we “believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based on information available to us as of the applicable date of this prospectus, free writing prospectus and documents incorporated by reference into this prospectus, and while we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted an exhaustive inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain and investors are cautioned not to unduly rely on these statements.

USE OF PROCEEDS

Except as described in any applicable prospectus supplement or in any free writing prospectuses we have authorized for use in connection with a specific offering, we intend to use the net proceeds from any offering pursuant to this prospectus to make investments in accordance with our investment objective and strategies, to pay our operating expenses and other cash obligations, and for general corporate purposes, including to repay or repurchase outstanding indebtedness, in which case the interest rate and maturity date of which will be described in a prospectus supplement or freewriting prospectus.

We anticipate that substantially all of the net proceeds of an offering of securities pursuant to this prospectus and its related prospectus supplement will be used for the above purposes within three months of any such offering, depending on the availability of appropriate investment opportunities consistent with our investment objective, but no longer than within six months of any such offerings.

Our ability to achieve our investment objective may be limited to the extent that the net proceeds from an offering, pending full investment, are held in interest-bearing deposits or other short-term instruments. See “Risk Factors—Risks Relating to Our Securities—We may be unable to invest a significant portion of the net proceeds from an offering or from exiting an investment or other capital on acceptable terms, which could harm our financial condition and operating results” in our most recently filed Annual Report on Form 10-K, as well as in subsequent filings with the SEC.

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PRICE RANGE OF COMMON STOCK

Our common stock is traded on the NYSE under the symbol “MAIN.”

The following table sets forth, for the periods indicated, the range of high and low closing prices of our common stock as reported on the NYSE, and the sales price as a percentage of the net asset value per share of our common stock.

On March 1, 2022, the last sale price of our common stock on the NYSE was $42.75 per share, and there were approximately 360 holders of record of the common stock which did not include stockholders for whom shares are held in “nominee” or “street name.” The net asset value per share of our common stock on December 31, 2021 (the last date prior to the date of this prospectus on which we determined our net asset value per share) was $25.29, and the premium of the March 1, 2022 closing price of our common stock was 77% to this net asset value per share.

Shares of BDCs may trade at a market price that is less than the value of the net assets attributable to those shares. The possibility that our shares of common stock will trade at a discount from net asset value per share or at premiums that are unsustainable over the long term are separate and distinct from the risk that our net asset value per share will decrease. It is not possible to predict whether our common stock will trade at, above, or below net asset value per share. Since our initial public offering in October 2007, our shares of common stock have traded at prices both less than and exceeding our net asset value per share.

MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

The information contained under the caption “Management’s Discussion and Analysis of Financial Condition and Results of Operations” of our most recent Annual Report on Form 10-K is incorporated by reference herein.

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PORTFOLIO COMPANIES

The following table sets forth certain unaudited information as of December 31, 2021 (dollars in thousands), for the portfolio companies in which we had a debt or equity investment. Other than these investments, our only formal relationships with our portfolio companies are the managerial assistance ancillary to our investments and the board observer or participation rights we may receive. As of December 31, 2021, none of our portfolio company investments constituted five percent or more of our total assets. The following table excludes our investments in marketable securities and idle funds investments.

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