|    |                                                                                                                          |
|----|--------------------------------------------------------------------------------------------------------------------------|
| 1) | I have reviewed this Quarterly Report on Form 10-Q/A of Costco Wholesale Corporation (“the registrant”); and |

|    |                                                                                                                                                                                                                                                                                                            |
|----|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 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. |

|                                                  |
|--------------------------------------------------|
|                                                  |  |
| /s/    W. CRAIG JELINEK |   |
| W. Craig Jelinek                                 |   |
| President, Chief Executive Officer and Director  |   |

----

|    |                                                                                                                          |
|----|--------------------------------------------------------------------------------------------------------------------------|
| 1) | I have reviewed this Quarterly Report on Form 10-Q/A of Costco Wholesale Corporation (“the registrant”); and |

|    |                                                                                                                                                                                                                                                                                                            |
|----|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 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. |

|                                                                                         |
|-----------------------------------------------------------------------------------------|
|                                                                                         |  |
| /s/    RICHARD A. GALANTI                                      |   |
| Richard A. Galanti                                                                      |   |
| Executive Vice President, Chief Financial Officer and Director |   |