Struggling Leeds ended a four-game losing run to dent Chelsea’s Premier League title charge.
The Blues dropped to fourth place – nine points behind leaders Arsenal – after a disappointing display at Elland Road.
With boss Daniel Farke under pressure, the hosts dominated the first half and struck twice through first Premier League goals for both Jaka Bijol and Ao Tanaka.
Chelsea rallied at the start of the second period and half-time substitute Pedro Neto pulled one back in the 50th minute, but Enzo Maresca’s men suffered a massive blow when they conceded a third in the 72nd minute after a defensive howler.
Tosin Adarabioyo’s mistake allowed Leeds striker Dominic Calvert-Lewin a tap-in to restore his side’s two-goal cushion and seal a desperately-needed second win in nine games to take them out of the bottom three.
It was a first win for Farke’s men over a team above 13th in the Premier League for more than three years, and came at a crucial time as their German manager faced growing frustration from the stands amid speculation about his future following their poor run of results.
Apart from Joao Pedro’s mis-hit effort, Liam Delap’s weak, poked shot in the 38th minute was their only effort on target before the interval.
Leeds doubled their lead two minutes before half-time when Enzo Fernandez was dispossessed near his own box and Jayden Bogle found Tanaka to fire in a powerful, swerving strike.
Maresca sent on Neto and Malo Gusto for Benoit Badiashile and Estevao Willian, who was fortunate to only get a yellow card, not red, for kicking out at Gabriel Gudmundsson.
But Lukas Nmecha and Calvert-Lewin had chances even before Neto volleyed in Jamie Gittens’ cross at the back post.
Chelsea sent on Cole Palmer, returning from a groin injury after more than two months out, and Alejandro Garnacho to spark their side, and the pair combined for a big chance in the 69th minute, but Palmer dragged his low shot wide.
While Chelsea were overtaken by Aston Villa in third place, Leeds moved up to 17th place and three points clear of West Ham, who visit Manchester United on Thursday.
