A brilliant goal from Eberechi Eze denied Chelsea a second consecutive Premier League victory.
Fresh from scraping through their Conference League qualifier despite defeat to Servette on Thursday, Enzo Maresca saw his team dominate Crystal Palace in the first half as he sought back-to-back league wins.
There appeared to be a smooth path to victory when Nicolas Jackson tucked away Cole Palmer's pass midway through the first half to hand the hosts the lead their football warranted.
Chances to add to their tally came and went and so it was against the run of play when Eze delicately curled Palace level early in the second period, placing the ball masterfully out of goalkeeper Robert Sanchez's reach to stun home fans in west London.
Chelsea had kept the ball patiently for the opening 10 minutes and went close with the game's first chance, Palmer taking possession 25 yards out from Wesley Fofana's pass, advancing into space and whipping an effort inches wide.
Adam Wharton replied in kind for Palace, driving low from outside the box with his left foot and forcing a save from Sanchez. It would be his team's only sight of goal during a half dominated by the hosts.
Chelsea were a whisker away from taking the lead after 20 minutes when defender Marc Guehi allowed a high ball from Fofana to drop over his shoulder and in through the gap stole Noni Madueke, opening up his body in search of the corner but sweeping wide.
Madueke went close again minutes later when he evaded Tyrick Mitchell and got his foot to Enzo Fernandez's fine raking ball only to be denied by a superb reaction save from Dean Henderson.
The goal came from an excellent Chelsea break. Levi Colwill dispossessed Guehi and fed Madueke who rocketed over the halfway line away from Will Hughes, slipping the ball down the right side of the box for Palmer.
Last season's top scorer made three assists during last weekend's 6-2 win over Wolves and he claimed another here, spotting Jackson at the far post and flicking it low back across goal for the striker to finish the move with an easy tap-in.
Henderson saved well from Palmer and Colwill in the first moments of the second half as Chelsea threatened a second but within minutes their lead was wiped out and spectacularly so.
Cheick Doucoure's thunderous drive hit Fofana and the ball broke to the edge of the box for Eze, who with a nonchalant right foot scooped it wide of Sanchez's dive and into the corner for 1-1.
Suddenly the game was taking place entirely in Chelsea's half and Palace looked the likelier to score a second.
Eze was inches from reaching a low cross ahead of Malo Gusto who saved his team with a superb sliding intervention, before Sanchez fumbled Daichi Kamada's driven effort through his hands, the goalkeeper fortunate to see the ball skip away from his grasp and behind.
Jackson drilled into the side netting in stoppage time when Joao Felix outside him looked a better option and was then denied one-on-one by another fine Henderson stop, as time ran out for Maresca's side.
