Westbrook headed to Texas in the off-season after 11 seasons with the Thunder, who led 60-48 at half-time and extended their lead in the final two quarters.
Danilo Gallinari top-scored for the Thunder with 23 while Shai Gilgeous-Alexander added 20.
Kevin Love hit a three-point jumpshot with less than a minute left in overtime as the Cleveland Cavaliers beat the Detroit Pistons 115-112.
He had 17 points on the night while Tristan Thompson top scored with 35, including two free-throws in the last minute of regulation to force the extra period.
The Philadelphia 76ers – without the injured Joel Embiid – came from behind to beat the Boston Celtics 109-98 and the Minnesota Timberwolves saw off Northwest rivals the Portland Trail Blazers 116-102.