CERTIFICATION

EXHIBIT 31.2

I, Michael D. Mulholland, certify
that:

| | 1. | I have reviewed this Annual Report on Form 10-K of Barrett Business Services,
                    Inc.;
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| | 2. | Based on my knowledge, this annual 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 annual report;
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| | 3. | Based on my knowledge, the financial statements, and other financial information
                    included in this annual 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 annual report;
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| | 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 we have:
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| | 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 is made known to us by others
               within the company, particularly during the period in which this annual report
               is being prepared;
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| | b. | evaluated the effectiveness of the Registrants disclosure controls and
               procedures and presented in this annual 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;
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| | 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;
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| | 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):
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| | 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
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| | 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.
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|                     |  |                                             
|-------------------- |  | --------------------------------------------
|Date: March 30, 2006 |  | /s/ Michael D. Mulholland                   
|                     |  | Michael D. MulhollandChief Financial Officer