<PAGE>

                                                                    EXHIBIT 31.2

      RULE 13a-14(a)/15d-14(a) CERTIFICATION OF PRINCIPAL FINANCIAL OFFICER

I, Jeffrey D. Gash, certify that:

      1.    I have reviewed the annual report on Form 10-K for the year ended
                  June 30, 2004 of Jaco Electronics, 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 registrant as of, and for,
                  the periods presented in this report;

      4.    The registrant'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 registrant and 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 registrant'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 registrant's
                        internal control over financial reporting that occurred
                        during the registrant's most recent fiscal quarter (the
                        registrant's fourth fiscal quarter in the case of an
                        annual report) that has materially affected, or is
                        reasonably likely to materially affect, the registrant'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 registrant's auditors and the
                  audit committee of the registrant's board of directors (or
                  persons performing the equivalent functions):

<PAGE>

                  (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 registrant'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 registrant's internal control over financial
                        reporting.

Date: September 28, 2004

                                               /s/ Jeffrey D. Gash
                                               ---------------------------------
                                               Jeffrey D. Gash
                                               Executive Vice President, Finance
                                               and Secretary
                                               (Principal Financial Officer)