It was Westbrook's first triple-double of the playoffs after posting 18 in the regular season. Kevin Durant added 26 points and 11 rebounds for Oklahoma City.
Golden State, which won a league record 73 games in the regular season, lost consecutive games for the first time this season. The Warriors must win Game 5 on Thursday in Oakland to keep their season alive.
Klay Thompson led Golden State with 26 points. Two-time league MVP Stephen Curry was limited to 19 points on 6-for-20 shooting.