Westbrook, who finished two assists short of his 19th triple-double of the season, scored eight points in the final 1:32 to help the Thunder win for the fifth time in the past six games.
Devin Booker had 39 points and eight assists, and Josh Jackson and TJ Warren had 19 points apiece for the Suns, who have lost 11 of 12. They broke a 10-game losing streak with a victory in Memphis on Wednesday.
Westbrook tied the game at 116 on a layup with 1:32 left, and his 3-pointer gave the Thunder a 119-116 lead with 55.9 seconds remaining.
After Jackson missed a long 3-pointer, Westbrook missed two shots but got the offensive rebound both times. The Thunder called a timeout with 22.5 seconds left.
Westbrook was fouled and made one of two free throws with 18.2 seconds remaining, and he sealed the game on a dunk after the Thunder stripped Booker at the other end.
The Suns have lost 19 of 22 since beating Oklahoma City in Phoenix on Jan. 7. The teams meet in the final game of the season series Wednesday in Oklahoma City.
Paul George had 20 points and Carmelo Anthony had 14 points and eight rebounds for the Thunder, who have won 14 of 21 while competing for a playoff spot in the tight Western Conference.
Westbrook remains three triple-doubles short of becoming the fourth player in NBA history to reach 100. Oscar Robertson (181), Magic Johnson (138) and Jason Kidd (107) are the top three.
Booker tied a season high with six 3-pointers, and he has scored 39, 34, 40, 30, 27 and 28 points in his last six games while making 23 threes. He missed the previous four games with a hip injury.
Suns center Alex Len had seven points, eight rebounds and six blocked shots. Phoenix made 11 of 22 3-point attempts.
Booker and Westbrook staged a tug-of-war in the first half, which ended with the Suns holding a 67-60 lead.
Booker had 21 points, eight assists and four rebounds while making 9 of 12 field-goal attempts before the break. Westbrook had 19 points, seven rebounds and four assists while making 7 of 12 shots from the field prior to halftime.
--Field Level Media
Oklahoma City | Phoenix | |
Russell Westbrook 43 | Scoring | Devin Booker 39 |
Russell Westbrook 8 | Assists | Devin Booker 8 |
Russell Westbrook 14 | Rebounds | Elfrid Payton 10 |
Russell Westbrook 9 | Free Throws Made | Elfrid Payton 6 |
Paul George 2 | Steals | Josh Jackson 2 |
Steven Adams 2 | Blocks | Alex Len 6 |
Team | Points | FG% | 3PM-3PA | FTM-FTA | Assists | Rebounds | Blocks | Steals | Turnovers |
Oklahoma City | 124 | 47.9 | 11-34 | 21-29 | 22 | 48 | 11 | 5 | 11 |
Phoenix | 116 | 47.9 | 11-25 | 13-18 | 26 | 44 | 12 | 5 | 15 |