EXHIBIT 10.21

                                October 17, 2002

Mercantile Bank Corporation
Mercantile Bank of West Michigan
5650 Byron Center Avenue SW
Wyoming, Michigan 49509

         Re:  Amendment to Employment Agreement dated October 18, 2001

Ladies and Gentlemen:

         This letter confirms our agreement reached today regarding the
Employment Agreement dated as of October 18, 2001 by and among you and me (the
"Employment Agreement"). We have agreed that Section 8.5(d) of the Employment
Agreement is amended effective immediately by deleting its current text and
substituting the following text in its place:

                  "(d) any term life insurance policies without any cash
         surrender value, or any term life insurance policies having a cash
         surrender value that is under $10,000 in aggregate amount, owned by the
         Bank or the Company and insuring the life of the Employee, to the
         extent they may be practically assigned or transferred to the Employee
         without any adverse affect on the Bank or the Company, and which upon
         assignment or transfer to the Employee the cash surrender value of the
         policy is paid by the Employee to the Bank or the Company, whichever is
         the owner of the policy, plus"

         I understand and agree that my execution of this letter is in part to
induce you to increase my annual base salary for 2003 under the Employment
Agreement, and to make the Employment Agreement more closely reflect our mutual
intent.

         Except as specifically amended by this letter, all of the terms of the
Employment Agreement remain in full force and effect. This letter may be
executed in counterparts, and is governed by Michigan law.

                                           /s/ Gerald R. Johnson, Jr.
                                           -----------------------------------
                                                         (signature)
                                           Gerald R. Johnson, Jr.
                                           -----------------------------------
                                           (print or type Employee's name)
MERCANTILE BANK CORPORATION

By: /s/ Michael H. Price
    ----------------------------------------
    Its: President & Chief Operating Officer

MERCANTILE BANK OF WEST MICHIGAN

By: /s/ Michael H. Price
    ----------------------------------------
     Its: President & Chief Executive Officer