Main Street Capital (MAIN) 10-K 2017 FY Annual report

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Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

       We have issued our reports dated February 23, 2018, with respect to the consolidated financial statements, financial highlights, financial statement schedule and internal control over financial reporting included in the Annual Report of Main Street Capital Corporation on Form 10-K for the year ended December 31, 2017. We consent to the incorporation by reference of said reports in the Registration Statements of Main Street Capital Corporation on Form S-8 (File Nos. 333-203893 and 333-208643).

/s/ GRANT THORNTON LLP

Houston, Texas
February 23, 2018

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Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM