Certification of the Chief Financial Officer under Rule 13a-14(a)
                                                                    EXHIBIT 31.2


I, Michael D. Mulholland, certify that:

  1.  I have reviewed  this  Quarterly  Report on Form 10-Q of Barrett  Business
      Services, Inc.;

  2.  Based on my knowledge,  this quarterly  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 quarterly report;

  3.  Based on my knowledge,  the consolidated  financial statements,  and other
      financial information included in this quarterly 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
      quarterly 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 quarterly report is being prepared;

           (b) Evaluated  the   effectiveness  of  the  Registrant's  disclosure
           controls and procedures  and presented in this  quarterly  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 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:

           (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:  August 15, 2005                    /s/ Michael D. Mulholland
                                          ---------------------------------
                                          Michael D. Mulholland
                                          Chief Financial Officer