Demand for Apple's flagship product has been slowing since the second quarter when the firm reported the first drop in iPhone sales since their 2007 launch.
The iPhone makes up for around two-thirds of Apple's sales and accounts for even more of its profits.
The slowdown in iPhone sales sent profit down 27% to $7.8bn in the three months to 25 June, while revenues fell 14.6% to $42.4bn.
Apple's sales in Greater China - defined by the company as China, Hong Kong and Taiwan - plunged 33%.
The firm blamed economic uncertainty and people not upgrading their phones as often for the drop.