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 Quarterly Report of UnionBancorp, Inc. (the
"Company") on Form 10-Q for the period ended June 30, 2006 as filed with the
Securities and Exchange Commission on August 11, 2006 (the "Report"), I, Scott
A. Yeoman, 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.


                                    /s/ SCOTT A. YEOMAN
                                    --------------------------------------
                                    Name:      Scott A. Yeoman
                                    Title:     President and
                                               Principal Executive Officer
                                    Date:      August 11, 2006

                                      36.