The retailer said it had $3.44 billion in net sales for the first quarter, below both analysts' estimates and the figure reported in the prior-year period. Gap also said it expects diluted earnings per share of 31 to 32 cents for the period, well short of Wall Street's expectations of 44 cents.
The stock dropped more than 10 percent in after-hours trading. It has fallen about 45 percent in the last year.
"They've been struggling for a while. I don't think it means that all retailers should be thrown out with it," said trader Karen Finerman, who added she would stay away from Gap's stock.