<PAGE>
                                  EXHIBIT 31.2

                  CERTIFICATION OF PRINCIPAL FINANCIAL OFFICER
                          PURSUANT TO RULE 13A-14(A) OF
                       THE SECURITIES EXCHANGE ACT OF 1934

I, Deborah F. Ricci, the principal financial officer of Hemagen Diagnostics,
Inc. certify that:

1.   I have reviewed this annual report on Form 10-KSB of Hemagen Diagnostics,
     Inc.;

2.   Based on my knowledge, this report does not contain any untrue statement of
     a material fact or omit to state a material fact necessary to make the
     statements made, in light of the circumstances under which such statements
     were made, not misleading with respect to the period covered by this
     report;

3.   Based on my knowledge, the financial statements, and other financial
     information included in this report, fairly present in all material
     respects the financial condition, results of operations and cash flows of
     the small business issuer as of, and for, the periods presented in this
     report;

4.   The small business issuer's other certifying officer and I are responsible
     for establishing and maintaining disclosure controls and procedures (as
     defined in Exchange Act Rules 13a-15(e) and 15d-15(e) for the small
     business issuer and we have:

     A.   Designed such disclosure controls and procedures or caused such
          disclosure controls and procedures to be designed under our
          supervision, to ensure that material information relating to the
          registrant, including its consolidated subsidiaries, is made known to
          us by others within those entities, particularly during the period in
          which this report is being prepared;

     B.   Evaluated the effectiveness of the small business issuer's disclosure
          controls and procedures and presented in this report our conclusions
          about the effectiveness of the disclosure controls and procedures, as
          of the end of the period covered by this report based on such
          evaluation; and

     C.   Disclosed in this report any change in the small business issuer's
          internal control over financial reporting that occurred during the
          small business issuer's most recent fiscal year that has materially
          affected, or is reasonably likely to materially affect, the small
          business issuer's internal control over financial reporting; and

5.   The registrant's other certifying officer and I have disclosed, based on
     our most recent evaluation of internal control over financial reporting, to
     the small business issuer's auditors and the audit committee of small
     business issuer's board of directors (or persons performing the equivalent
     functions):

     A.   All significant deficiencies and material weaknesses in the design or
          operation of internal control over financial reporting which are
          reasonably likely to adversely affect the small business issuer's
          ability to record, process, summarize and report financial
          information; and

     B.   Any fraud, whether or not material, that involves management or other
          employees who have a significant role in the small business issuer's
          internal control over financial reporting; and


Date: December 23, 2005                 /s/ Deborah F. Ricci
                                        ----------------------------------------
                                        Deborah F. Ricci
                                        Principal Financial Officer