CUPERTINO, Calif.—Apple Inc. has bought $14 billion of its own shares in the two weeks since reporting financial results that disappointed Wall Street, Chief Executive Tim Cook said in an interview.

Mr. Cook said Apple was "surprised" by the 8% decline in its shares on Jan. 28, the day after it reported lower iPhone sales than projected and warned that revenue in the current quarter might decline from the same period a year ago. Mr. Cook said he wanted to be "aggressive" and "opportunistic."

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