Exhibit (n)(1)
CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM
We have issued our reports dated March 12, 2009 with respect to the consolidated financial
statements, internal control over financial reporting and Schedule 12-14 and our report dated April
24, 2009 with respect to the schedule of Senior Securities of Main Street Capital Corporation
contained in Amendment No. 2 to the Registration Statement and Prospectus. We consent to the use of
the aforementioned reports in Amendment No. 2 to the Registration Statement and Prospectus, and to
the use of our name as it appears under the caption Independent Registered Public Accounting
Firm.
/s/ GRANT THORNTON LLP
Houston, Texas
April 24, 2009