Apple reported the slowest growth in iPhone sales since the product's 2007 launch and warned sales will decline.
The US tech giant sold 74.8 million iPhones in its fiscal first quarter, compared with 74.5 million a year ago.
Apple said revenue for the next quarter would be between $50bn-$53bn, below the $58bn it reported a year ago.
This would mark Apple's first fall in revenues since it launched the iPhone.
Apple boss Tim Cook credited "all-time record sales of iPhone, Apple Watch and Apple TV" for the performance.
Chief financial officer, Luca Maestri, said the company was operating in "a very difficult macroeconomic environment". He added that "units will decline in the quarter" and that the company was not projecting beyond those 3 months.