A controversial penalty, scored by Cesc Fabregas, denied West Ham a first win at Chelsea in 14 years.
Fabregas converted an 89th-minute spot-kick to earn a 2-2 draw after referee Bobby Madley adjudged that Ruben Loftus-Cheek had been tripped by Michail Antonio. Replays suggested that if there was contact it was minimal and outside the area.
Andy Carroll thought he had enhanced the Hammers' bid for Champions League qualification when he scored a minute after coming off the bench, but Fabregas scored his second after his brilliant free-kick had earlier cancelled out Manuel Lanzini's superb opener.
West Ham remain fifth, one point behind Manchester City and without a double over Chelsea since the 2002-03 season, while the Blues' unbeaten league run was extended to 14 games, 13 of them under interim boss Guus Hiddink.
Chelsea were aiming to recover from two cup exits in four days, the second of which saw Diego Costa dismissed. The suspended striker was replaced by Loic Remy, who made his first start since September.
Chelsea's FA Cup exit at Everton followed the Champions League loss to Paris St Germain, while the Hammers are bidding to play Europe's elite at the Olympic Stadium next term.
They made a fine start against Chelsea, pressing their derby rivals into a mistake that led to the opening goal.
Gary Cahill was caught in no-man's land when Diafra Sakho headed the ball on, and after John Obi Mikel slid in on Dimitri Payet the ball broke for Lanzini, who picked his spot.
Payet drove a shot just wide as the visitors continued to apply pressure before Cahill pleaded for a handball against Enner Valencia. Replays showed the ball hit the West Ham forward's shoulder.
West Ham had Chelsea back-pedalling again when Sakho and Lanzini released Aaron Cresswell, who had got forward from left back. Branislav Ivanovic made a last-ditch block.
Willian went close with a free-kick before Chelsea equalised when Fabregas curled in from 25 yards after Winston Reid had fouled Oscar.
Chelsea thought Adrian had handled the ball outside the area as the hosts poured forward at the start of the second half.
Ivanovic, at right-back as a fit-again John Terry made his first start in seven games and his 701st Chelsea appearance, rampaged down the flank and crossed for Oscar, who was unable to find the finish.
Pedro, on at half-time for Kenedy, next found Remy, who turned and forced Adrian to collect his shot at the second attempt.
Chelsea were caught as they pressed forward. Carroll made an arcing run behind Ivanovic and stayed onside as Cahill and Terry appealed.
Payet found him and Carroll did the rest -- but Chelsea continued to threaten. Substitute Bertrand Traore and Oscar had shots blocked, and Fabregas headed off target from a corner and then acrobatically fired over.
Traore cleared a Carroll header off the line from a corner before Loftus-Cheek broke and went down in the box and Fabregas converted.
Payet had a free kick saved after a squabble involving all 20 outfield players and Loftus-Cheek fired wide as both sides tried to find a winner.