Miami led 71-66 with 10:06 remaining in the fourth quarter, but the Thunder went on a 10-0 run to take command on the way to their seventh win in their last eight games.
Westbrook led the Thunder with a game-high 29 points, 13 rebounds and eight assists. Steven Adams had 24 points and 12 rebounds, Paul George scored 12 points and Raymond Felton added 10 off the bench, including eight in the fourth quarter for the Thunder.
James Johnson led the Heat with 23 points and Goran Dragic had 20. Justise Winslow and Wayne Ellington each added 14.
The Thunder outscored Miami 41-33 in the final period.
The Thunder have won six of the last seven meetings between the teams and four straight at home.
The contest was the first this season between the two squads, who will play again in Miami on April 9.
With the loss, Miami's hold on seventh place in the Eastern Conference was trimmed to a half game after Milwaukee beat Chicago on Friday night.
Both teams started out cold from the floor, but the Thunder went on an 8-0 run midway through the first quarter while Miami went scoreless for four and a half minutes and shot just 33 percent.
Miami's four three-pointers in the first quarter gave the Heat 809 for the season, breaking the team record of 808 set last year.
In a low-scoring second quarter, Alex Abrines gave the Thunder its largest lead at 12 points when he drained a three with 5:58 left before halftime.
However, Miami trimmed the lead to 44-40 behind a late five-point run.
Each team shot under 40 percent in the first half.
Dragic scored 13 points in the third quarter as Miami went on a 10-3 run over the final three minutes to take a 66-64 lead into the final period.
--Field Level Media
Miami | Oklahoma City | |
James Johnson 23 | Scoring | Russell Westbrook 29 |
Goran Dragic 5 | Assists | Russell Westbrook 8 |
Bam Adebayo 7 | Rebounds | Russell Westbrook 13 |
James Johnson 7 | Free Throws Made | Russell Westbrook 9 |
Goran Dragic 1 | Steals | Corey Brewer 2 |
Justise Winslow 1 | Blocks | Jerami Grant 1 |
Team | Points | FG% | 3PM-3PA | FTM-FTA | Assists | Rebounds | Blocks | Steals | Turnovers |
Miami | 99 | 39.1 | 13-30 | 18-20 | 22 | 41 | 1 | 4 | 12 |
Oklahoma City | 105 | 42.9 | 8-26 | 25-33 | 17 | 51 | 1 | 7 | 11 |