Analysts on average were expecting the largest U.S. warehouse club operator's same-store sales to rise 11.2 percent, according to Thomson Reuters data.
Same-store sales at U.S. locations increased 6 percent, while international sales rose 29 percent.
Excluding the impact of gasoline price increase and strong foreign currencies, comparable sales for April rose 4 percent.
Issaquah, Washington-based Costco said net sales for the four weeks ended May 2 rose 13 percent to $5.83 billion.
Shares of the company closed at $60.36 Wednesday on Nasdaq.
(Reporting by Anuradha Ramanathan in Bangalore; Editing by Vinu Pilakkott)