Exhibit 10.1

FIFTH AMENDMENT TO CREDIT AGREEMENT

THIS AMENDMENT TO CREDIT AGREEMENT (this “Amendment”) is entered into as of August 22, 2008, by and between BARRETT BUSINESS SERVICES, INC., a Maryland corporation (“Borrower”), and WELLS FARGO BANK, NATIONAL ASSOCIATION (“Bank”).

RECITALS

WHEREAS, Borrower is currently indebted to Bank pursuant to the terms and conditions of that certain Credit Agreement between Borrower and Bank dated as of July 1, 2005, as amended from time to time (“Credit Agreement”).

WHEREAS, Bank and Borrower have agreed to certain changes in the terms and conditions set forth in the Credit Agreement and have agreed to amend the Credit Agreement to reflect said changes.

NOW, THEREFORE, for valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereto agree that the Credit Agreement shall be amended as follows:

1. Section 1.1 (b) is hereby deleted in its entirety, and the following substituted therefor:

“(b) Letter of Credit Subfeature. As a subfeature under the Line of Credit, Bank agrees from time to time during the term thereof to issue or cause an affiliate to issue standby letters of credit for the account of Borrower (each, a “Letter of Credit” and collectively, “Letters of Credit”). The form and substance of each Letter of Credit shall be subject to approval by Bank, in its sole discretion. Each Letter of Credit shall be issued for a term acceptable to the Bank which, shall not exceed one (1) year and shall not have an expiration date more than one (1) year beyond the maturity date of the Line of Credit subject to any automatic extension clause that may be included in a Letter of Credit at the Bank’s discretion. The undrawn amount of all Letters of Credit shall be reserved under the Line of Credit and shall not be available for borrowings thereunder. Each Letter of Credit shall be subject to the additional terms and conditions of the Letter of Credit agreements, applications and any related documents required by Bank in connection with the issuance thereof. Each drawing paid under a Letter of Credit shall be deemed an advance under the Line of Credit and shall be repaid by Borrower in accordance with the terms and conditions of this Agreement applicable to such advances; provided however, that if advances under the Line of Credit are not available, for any reason, at the time any drawing is paid, then Borrower shall immediately pay to Bank the full amount drawn, together with interest thereon from the date such drawing is paid to the date such amount is fully repaid by Borrower, at the rate of interest applicable to advances under the Line of Credit. In such event Borrower agrees that Bank, in its sole discretion, may debit any account maintained by Borrower with Bank for the amount of any such drawing.”

2. Except as specifically provided herein, all terms and conditions of the Credit Agreement remain in full force and effect, without waiver or modification. All terms defined in the Credit Agreement shall have the same meaning when used in this Amendment. This Amendment and the Credit Agreement shall be read together, as one document.

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3. Borrower hereby remakes all representations and warranties contained in the Credit Agreement and reaffirms all covenants set forth therein. Borrower further certifies that as of the date of this Amendment there exists no Event of Default as defined in the Credit Agreement, nor any condition, act or event which with the giving of notice or the passage of time or both would constitute any such Event of Default.

UNDER OREGON LAW, MOST AGREEMENTS, PROMISES AND COMMITMENTS MADE BY BANK CONCERNING LOANS AND OTHER CREDIT EXTENSIONS WHICH ARE NOT FOR PERSONAL, FAMILY OR HOUSEHOLD PURPOSES OR SECURED SOLELY BY THE BORROWER’S RESIDENCE MUST BE IN WRITING, EXPRESS CONSIDERATION AND BE SIGNED BY BANK TO BE ENFORCEABLE.

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the day and year first written above.

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