Exhibit 99.1

Press Release

COSTCO WHOLESALE CORPORATION REPORTS THIRD QUARTER AND YEAR-TO-DATE

OPERATING RESULTS FOR FISCAL YEAR 2016

ISSAQUAH, Wash., May 25, 2016 - Costco Wholesale Corporation (“Costco” or the “Company”) (Nasdaq: COST) today announced its operating results for the third quarter (twelve weeks) and first thirty-six weeks of fiscal 2016, ended May 8, 2016.

Net sales for the quarter increased two percent, to $26.15 billion from $25.52 billion last year. Net sales for the first thirty-six weeks increased two percent, to $80.34 billion from $78.67 billion last year.

Comparable sales for the twelve-week and thirty-six-week periods were as follows:

Comparable sales for these periods excluding the negative impacts from gasoline price deflation and foreign exchange were as follows:

Net income for the quarter was $545 million, or $1.24 per diluted share, compared to $516 million, or $1.17 per diluted share, last year. Net income for the thirty-six weeks was $1.57 billion, or $3.56 per diluted share, compared to $1.61 billion, or $3.64 per diluted share, last year. Net income for the thirty-six-week period last year was positively impacted by $43 million ($0.10 per diluted share) in net nonrecurring income tax benefits.

Costco currently operates 705 warehouses, including 493 in the United States and Puerto Rico, 90 in Canada, 36 in Mexico, 27 in the United Kingdom, 25 in Japan, 12 in Korea, 12 in Taiwan, eight in Australia and two in Spain. Costco also operates electronic commerce web sites in the U.S., Canada, the United Kingdom, Mexico, Korea and Taiwan.

A conference call to discuss these fiscal 2016 third quarter operating results is scheduled for 8:00 a.m. (PT) on May 26, 2016, and is available via a webcast on www.costco.com (click on Investor Relations and “Play Webcast”).

Press Release

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, consumer and small business spending patterns and debt levels, breaches of security or privacy of member or business information, conditions affecting the acquisition, development, ownership or use of real estate, capital spending, actions of vendors, 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. Forward-looking statements speak only as of the date they are made, and we do not undertake to update these statements, except as required by law.

CONTACTS: Costco Wholesale Corporation

        Richard Galanti, 425/313-8203

        Bob Nelson, 425/313-8255

        Jeff Elliott, 425/313-8264

Press Release

COSTCO WHOLESALE CORPORATION

CONDENSED CONSOLIDATED STATEMENTS OF INCOME

(dollars in millions, except per share data)

(unaudited)

Press Release

COSTCO WHOLESALE CORPORATION

CONDENSED CONSOLIDATED BALANCE SHEETS

(amounts in millions, except par value and share data)

(unaudited)

Subject to Reclassifications