Mavericks All-Star forward Nowitzki, who scored 24 points and grabbed 11 rebounds, hit a driving lay-up with three seconds left to provide the wining margin.
Miami's Dwyane Wade launched a 28-foot, three-point attempt at the buzzer but it hit the back of the rim, eliciting a collective groan from the 20,000 at American Airlines Arena.
"Defensively we really got up, into them, started to pressure the full court, and then we scrambled defensively," Nowitzki said.
"We even gave up some second, offensive rebounds but we kept scrambling offensively.
"When we get some stops we can move and we can play off the flow."
The best-of-seven series shifts to Dallas for the next three games, with Game Three set for Monday morning (AEST) at the American Airlines Centre.
Miami looked to have seized control of the game with a 13-0 run in the fourth quarter that padded its two-point advantage into a 88-73 lead with just over seven minutes left.
Wade, who scored 36 points on a variety of long jump shots, running one-handers and fast breaks, scored nine points during the run, triggering a party atmosphere in South Florida.
But the resilient Mavericks embarked on a 20-2 run of their own and Nowitzki's 25-foot three-pointer with 26 seconds left gave them a 93-90 lead.
Miami reserve guard Mario Chalmers responded with a three-pointer just two seconds later, setting the stage for Nowitzki's heroics.
"Hang out. Hang around. Keep believing," Dallas coach Rick Carlisle said.
"This team has been through some difficult situations. We've been down big a couple of times in the Playoffs.
"We have shown that we have the ability to come back and the guys believe that if we get stops, we'll always give ourselves a chance. It wasn't gonna happen unless we got stops."
Nowitzki, who injured a tendon in the middle finger of his left hand in the first game of the series, struggled early and hit three of his first 10 shots.
But he recovered in the second half, making 10 of 22 shots for the game.
"All year our guys have believed," Carlisle said.
"And tonight was another good example. They had to win the game. It wasn't easy."
Heat coach Erik Spoelstra said the defeat was one of the toughest he has had to endure.
"No question about it, that's about as tough a fourth quarter you can have. When it started to slide, it just kept on going," he said.
"Really, I think offensively if we could have executed and moved the ball, we might have been able to stem the tide a little bit, even as poor as we were defensively down the stretch.
"It was highly uncharacteristic for us on both ends of the court.
"But we're a resilient group. By the time we get on that plane tomorrow, we'll get our minds and body and spirit ready for Game Three.
"This is a long series. So we're not happy about what happened, but we've got an opportunity in Game Three."
-Reuters
Tags: sport, basketball, united-states First posted June 3, 2011 14:25:00