Analysts surveyed by Thomson Reuters predicted a 3.3 percent increase. Costco shares rose in early premarket trading.
Sales at stores open at least a year are closely watched as a key indicator of a retailer's health. They exclude results from stores recently opened or closed.
Costco Wholesale Corp. said Thursday that the figure climbed 5 percent in the U.S. for the four weeks ended Feb. 2. Internationally, the metric edged up 1 percent.
Removing the impact of lower gas prices and foreign currency fluctuations, sales at stores open at least a year rose 6 percent. In the U.S. the figure rose 5 percent, while overseas it increased 8 percent.
Total revenue climbed 6 percent to $7.99 billion.
For the year to date, Costco's sales at stores open at least a year increased 3 percent. The metric rose 4 percent in the U.S. and climbed 1 percent abroad.
Excluding the impact of lower gas prices and foreign currency fluctuations, sales at stores open at least a year rose 5 percent. The figure also climbed 5 percent in the U.S. and gained 7 percent overseas.
Total revenue for the year to date increased 6 percent to $46.32 billion.
Costco, which is based in Issaquah, Wash., said that it plans to report its fiscal second-quarter financial results on March 6.
The company currently runs 649 warehouses, including 462 in the U.S. and Puerto Rico, 87 in Canada, 33 in Mexico, 25 in the U.K., 18 in Japan, 10 in Taiwan, nine in Korea and five in Australia.
Its shares rose $1.87, or 1.7 percent. To $112.38 in premarket trading about three hours ahead of the market open.