Bam Adebayo put Miami in front for good on a put-back dunk with 1:15 remaining in overtime and finished with 18 points, 11 rebounds and 10 assists for his second triple-double in three games.
Without Doncic, Tim Hardaway Jr. scored 18 of his 28 points in the second half to help Dallas rally, but was shut out in overtime.
Kristaps Porzingis, the other half of Dallas’ star European pairing with Doncic, had 22 points and 14 rebounds but couldn’t convert on two possessions late in the extra period. Then the 7-foot-3 Latvian gave up an offensive rebound after Jimmy Butler missed two free throws with nine seconds remaining.
With another chance after another foul, Butler made two free throws for a three-point lead, and Jalen Brunson missed a 3-pointer just before the buzzer.
Butler led Miami with 27 points, and Tyler Herro scored 19 as the Heat again avoided back-to-back losses for the first time this season. They were playing a night after a 113-110 loss to LeBron James and the Lakers at home.
Doncic’s right foot landed on the foot of Heat guard Kendrick Nunn on a drive less than two minutes into the game.
The reigning rookie of the year lost control of the ball for a turnover and limped off the court before going down behind the basket while play continued at the other end. He got up a short time later but went straight to the locker room. The team said X-rays were negative, but he didn’t return.
The Mavericks trailed by four when Doncic went down and the deficit ballooned to 19 in about five minutes and reached 24 in the second quarter.
But Dallas wiped out a 23-point halftime deficit and the led twice in the fourth quarter, including 112-108 before the Heat scored the final four points of regulation.
Hardaway missed a runner in the final seconds of regulation before Butler misfired on a pull-up 3-pointer at the buzzer.
Porzingis gave a stunned crowd the first chance to cheer by making a 3-pointer from the logo at center court to beat the first-quarter buzzer.
Doncic was playing two nights after the 20-year-old dazzled the crowd in Mexico City with a pre-game speech in Spanish before scoring 41 points with 12 rebounds and 11 assists in a 122-111 victory over Detroit. It was his NBA-leading eighth triple-double of the season.
The Slovenian guard entered the game averaging 30.4 points, 9.9 rebounds and 9.3 assists per game while leading the resurgent Mavericks to the Southwest Division lead.
Heat: Miami has won five straight games in the series. … Butler extended his streak of games with at least 20 points to eight, the longest since Dwyane Wade had eight in March 2015. … Adebayo also had two blocks. … Kelly Olynyk had 17 points and eight rebounds. Nunn scored 13.
Mavericks: Delon Wright returned after missing two games with a right abductor strain, going scoreless in nine minutes. … Brunson had 18 points, eight assists and seven rebounds. … Maxi Kleber, whose dunk gave Dallas its first lead with 4:28 remaining, scored 17 points on 7-of-9 shooting.
Heat: Three-game trip continues with middle game at Memphis on Monday. Miami has a franchise-best five-game winning streak against the Grizzlies.
Mavericks: At Milwaukee on Monday. The Bucks swept the two-game series last season.