Exhibit (n)(1)
CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM
We have issued our reports dated March 18, 2008 (except for Note A2, as to which the date is
November 26, 2008) with respect to the consolidated financial statements and Schedule 12-14 and our
report dated November 26, 2008 with respect to the schedule of Senior Securities of Main Street
Capital Corporation contained in the Registration Statement and Prospectus. We consent to the use
of the aforementioned reports in the Registration Statement and Prospectus, and to the use of our
name as it appears under the caption Experts.
/s/ GRANT THORNTON LLP
Houston, Texas
November 26, 2008