Jose Mourinho suffered only his second defeat in his 100th home league game in charge of Chelsea as Crystal Palace claimed a shock win at Stamford Bridge.
After a goalless first half in which Chelsea dominated possession, Palace took the lead when Bakary Sako drove in after Yannick Bolasie’s low cross.
Chelsea responded when substitute Radamel Falcao headed in his first goal for the club.
Palace regained the lead immediately as Joel Ward stabbed in a late winner.
Chelsea, the reigning Premier League champions, are now eight points behind leaders Manchester City after four games.
They have been far from convincing so far this season having collected just four points, with only one of those picked up on home soil.
Mourinho called the 3-0 loss to Manchester City “a fake result” but it is hard to argue that Palace were not good value for this win.
Alex McCarthy produced a fine double-save to deny Diego Costa and Cesc Fabregas in the first half, but otherwise the hosts were restricted to few clear-cut chances.
Cahill returned to the Chelsea starting XI in place of the suspended John Terry, while Crystal Palace brought Connor Wickham in for Glenn Murray up front, and the centre-back came under pressure early on as the visitors started brightly.
Chelsea eventually settled and Pedro came close to marking his home debut with a goal when he fired just wide with a curling effort after switching onto his left foot.
Kurt Zouma’s half-hearted appeal for a penalty following a tussle with Wickham went unrewarded, before Sako drew a diving save from goalkeeper Thibaut Courtois at the other end.
Palace continued to enjoy the better chances – Yohan Cabaye missing a glorious opportunity to break the deadlock just short of the hour mark.
When the ball found Cabaye at the edge of the box, the France international had the whole goal to aim at but placed his effort too close to a grateful Courtois.