One area of weakness for Apple in the quarter was the Greater China segment — comprising mainland China, Taiwan and Hong Kong. Revenue for that region fell 26 percent year over year to $12.49 billion. Previously, that area had posted consistent growth for Apple.
Still, "we feel good about China," Cook told CNBC earlier this week.
"We remain very optimistic about the China market over the long term, and we are committed to investing there for the long run," Apple CFO Luca Maestri said Tuesday.
Icahn noted he called Cook to tell him he exited the position.
The activist investor purchased his Apple stake in 2013. He previously told CNBC buying into the company was a "no-brainer."
Last May, Icahn said he had a $240 per share price target on Apple when it traded around $130 per share. As recently as September, Icahn told CNBC he considered buying more of the company's stock, saying it looked cheap.
— CNBC's Everett Rosenfeld contributed to this report.