EXHIBIT 32.1

The following certification is provided by the undersigned President and
Principal Executive Officer of UnionBancorp, Inc. on the basis of such officer's
knowledge and belief for the sole purpose of complying with 18 U.S.C. Section
1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.

                                  CERTIFICATION
                                  -------------

In connection with the Annual Report of UnionBancorp, Inc. (the "Company") on
Form 10-K for the period ended December 31, 2004 as filed with the Securities
and Exchange Commission on March 29, 2005 (the "Report"), I, Dewey R. Yaeger,
President and Principal Executive Officer of the Company, hereby certify,
pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the
Sarbanes-Oxley Act of 2002, that:

         (1)      The Report fully complies with the requirements of Section
                  13(a) of the Securities Exchange Act of 1934, as amended; and

         (2)      The information contained in the Report fairly presents, in
                  all material respects, the financial condition and results of
                  operations of the Company.


                      ------------------------------------
                              Name: Dewey R. Yaeger
                              Title: President and
                           Principal Executive Officer
                              Date: March 29, 2005