EXHIBIT 32.1

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

This certification is provided pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, 18 U.S.C. § 1350, and accompanies the quarterly report on Form 10-Q for the quarter ended March 31, 2020 (the "Form 10-Q") of Mercantile Bank Corporation (the "Issuer").

I, Robert B. Kaminski, Jr., President and Chief Executive Officer of the Issuer, certify that to my knowledge:

(i) the Form 10-Q fully complies with the requirements of Section 13(a) or Section 15(d) of the Securities Exchange Act of 1934; and

(ii) the information contained in the Form 10-Q fairly presents, in all material respects, the financial condition and results of operations of the Issuer.

Dated: May 11, 2020

/s/ Robert B. Kaminski, Jr.

Robert B. Kaminski, Jr.

President and Chief Executive Officer