Net income rose to $496 million, or $1.12 per share, for the first quarter ended Nov. 23, from $425 million, or 96 cents per share, a year earlier.
Net sales rose 7 percent to $26.28 billion. Total revenue, which includes membership fees, rose 7 percent to $26.87 billion.
Read MoreCostco to enter China through Alibaba's Tmall
Analysts on average expected a profit of $1.09 per share on revenue of $26.92 billion, according to Thomson Reuters I/B/E/S.
Up to Tuesday's close of $143.04, shares of the Issaquah, Washington-based company had risen 20 percent this year. The Nasdaq Composite Index had risen 12.6 percent.
The company said last week that it saw a 7 percent increase in net sales this November—to $9.43 billion—compared to the prior year, and that comparable traffic had grown 5 percent. International comp sales decreased by 1 percent.
Costco's stock is up 30 percent since its 2014 low of $109.50 in February, closing Tuesday at more than $143 a share.
During this quarter, the retailer said it would enter the Chinese market by selling its wares through Alibaba's online Tmall Global marketplace. That would allow Costco to introduce offerings to mainland China while outsourcing most of the related logistics.
—CNBC's Everett Rosenfeld contributed to this report.