Diego Costa smashed an 89th minute winner as the Blues began the Premier League season with a victory in a tight London derby at Stamford Bridge.
Chelsea almost dot frustrated despite dominating for long periods when James Collins struck to cancel out Eden Hazard’s penalty, but centre-forward Diego Costa was on hand to hit a late, late winner and hand Antonio Conte a perfect start in English football.
Chelsea started brightly and dominated the visitors for long periods but struggled to break through, only for Cesar Azpilicueta to be awarded a spot kick when he was tripped by Michail Antonio just after the break.
Hazard duly converted and Chelsea looked comfortable, only for West Ham to score with their only effort on target 15 minutes from time when Collins hammered home at a corner.
Diego Costa found space 20 yards out and hammered home to ensure all three points stayed in west London.
With the all teams having played their opener match, Chelsea follow Liverpool and Manchester United footprints to begin their chase for premier league champions.