The defender took advantage of sloppy marking to find space in the box and steer home Wesley Sneijder's inswinging corner on 65 minutes.
Fernando Torres had silenced a raucous crowd when he fired Chelsea into a ninth-minute lead and the Premier League leaders controlled the first half.
But the Turkish side improved after the break and Selcuk Inan was guilty of a bad miss from close range minutes before Chedjou's goal.
(Editing by Justin Palmer)
