Exhibit 99.1

COSTCO WHOLESALE CORPORATION REPORTS THIRD QUARTER AND YEAR-TO-DATE OPERATING RESULTS FOR FISCAL YEAR 2012

ISSAQUAH, Wash., May 24, 2012 – Costco Wholesale Corporation (“Costco” or the “Company”) (Nasdaq: COST) announced today its operating results for the third quarter (twelve weeks) and first thirty-six weeks of fiscal 2012, both ended May 6, 2012.

Net sales for the quarter increased eight percent, to $21.85 billion, from $20.19 billion last year. Net sales for the first thirty-six weeks increased ten percent, to $65.54 billion, from $59.46 billion last year.

Comparable sales were as follows:

Inflation in gasoline prices had a positive impact on comparable sales, particularly for the thirty-six-week period; foreign currencies had a negative impact for both periods. Excluding these effects, comparable sales were as follows:

Net income for the quarter was $386 million, or $.88 per diluted share, compared to $324 million, or $.73 per diluted share, last year. Net income for the first thirty-six weeks was $1.100 billion, or $2.50 per diluted share, compared to $984 million, or $2.22 per diluted share, last year. The quarter this year included a $6.5 million pre-tax LIFO charge ($.01 per diluted share) compared to a $49 million pre-tax LIFO charge ($.07 per diluted share) last year.

Costco currently operates 602 warehouses, including 435 in the United States and Puerto Rico, 82 in Canada, 32 in Mexico, 22 in the United Kingdom, 13 in Japan, eight in Taiwan, seven in Korea and three in Australia. The Company also operates Costco Online, an electronic commerce web site, at www.costco.com and at www.costco.ca in Canada. The Company plans to open up to an additional six new warehouses prior to the end of its fiscal year on September 2, 2012.

A conference call to discuss these third quarter operating results is scheduled for 8:00 a.m. (PT) today, May 24, 2012, and is available via a webcast on www.costco.com (click on Investor Relations and “Play Webcast”).

Certain statements contained in this document constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. For these purposes, forward-looking statements are statements that address activities, events, conditions or developments that the Company expects or anticipates may occur in the future. Such forward-looking statements involve risks and uncertainties that may cause actual events, results or performance to differ materially from those indicated by such statements. These risks and uncertainties include, but are not limited to, domestic and international economic conditions, including exchange rates, the effects of competition and regulation, uncertainties in the financial markets, and consumer and small business spending patterns and debt levels, conditions affecting the acquisition, development, ownership or use of real estate, actions of suppliers, rising costs associated with employees (including health care costs), energy and certain commodities, geopolitical conditions, and other risks identified from time to time in the Company’s public statements and reports filed with the Securities and Exchange Commission.

CONTACTS: Costco Wholesale Corporation

Richard Galanti, 425/313-8203, Bob Nelson, 425/313-8255, Jeff Elliott, 425/313-8264

COSTCO WHOLESALE CORPORATION

CONDENSED CONSOLIDATED STATEMENTS OF INCOME

(dollars in millions, except per share data)

(unaudited)

COSTCO WHOLESALE CORPORATION

CONDENSED CONSOLIDATED BALANCE SHEETS

(dollars in millions)

(unaudited)

Subject to Reclassifications