Harden made 1 of 2 free throws before Trey Burke made a 3-pointer to get the Mavericks within 3 with about 15 seconds left in OT. Harden made 1 of 2 free throws after that, Burke missed a 3, and Harden got the rebound to secure the victory.
Dallas led by 3 before Harden made the first of two free throws, and Robert Covington tipped in a miss on the second to tie it with 3.3 seconds remaining in regulation.
Luka Doncic missed a shot at the buzzer that would have won it for Dallas.
Kristaps Porzingis had 39 points and 16 rebounds for Dallas, and Doncic had a triple-double with 28 points 13 rebounds and 10 assists.
Porzingis put the Mavericks up four early in overtime. Houston scored the next eight points, with the last five from Harden, to take a 147-143 lead.
Porzingis had a three-point play, but Robert Covington added a 3-pointer after missing his first eight to extend Houston’s lead to four.
Harden, who had 23 points in the first quarter, passed Calvin Murphy to become the second-leading scorer in franchise history behind Hakeem Olajuwon.
Harden made two free throws with a minute left in the fourth to cut the lead to four, but Maxi Kleber made a 3-pointer on the other end to extend the lead to 138-131.
Harden cut the lead again seconds later with a 3-pointer with 40 seconds to go.
Covington got the Rockets within 2 points with two free throws. The Rockets were forced to foul, and Seth Curry made 1 of 2 free throws to leave Dallas up 139-136 with 5.2 seconds to go.
Westbrook added 31 points for the Rockets after arriving to Florida late after testing positive for the coronavirus.
The teams combined for the most first-half points in the NBA this season, with Dallas leading 85-75 to tie its franchise record.
The Rockets went on a 7-0 run, with four points from Westbrook, to trim the deficit late in the third quarter. But Dallas wrapped up the third with a 6-2 run to lead 119-108 entering the fourth quarter.
Watch James Harden drop 49, lead Rockets past Mavericks in OT originally appeared on NBCSports.com