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Exhibit 32.2

Certification of Chief Financial Officer
Pursuant to
Section 906 of the Sarbanes-Oxley Act of 2002 (18 U.S.C. 1350)

        In connection with the Quarterly Report of Main Street Capital Corporation (the "Registrant") on Form 10-Q for the quarter ended September 30, 2018 (the "Report"), as filed with the Securities and Exchange Commission on the date hereof, I, Brent D. Smith, the Chief Financial Officer of the Registrant, hereby certify, pursuant to 18 U.S.C. §1350, as adopted pursuant to §906 of the Sarbanes-Oxley Act of 2002, that:

  /s/ BRENT D. SMITH

  Name:   Brent D. Smith

  Date:   November 2, 2018



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Certification of Chief Financial Officer Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 (18 U.S.C. 1350)