Bosh, who was received by a chorus of boos during team introductions, scored 13 of his 28 points in the fourth quarter as the Heat defeated the Raptors 100-85 on Sunday for their 10th consecutive victory over Toronto.
"I was hearing a lot from the fans," said Bosh, who departed for Miami in a sign-and-trade deal in the 2010 off-season. "I thank them for continuing to stay on me and call me names and stuff because that helped my focus a lot. I was like 'I need to get in this to shut them up.'"
LeBron James poured in a game-high 30 points, while Dwyane Wade added 23 points for the Heat (30-14).
The loss spoiled strong efforts by new Raptors forward Rudy Gay, who scored 29 points, and DeMar DeRozan, who added 27.
"I wouldn't say I'm 100 per cent comfortable," said Gay, two days after joining his new team. "I'm still feeling my way out there. I still think this is a game we could've won. We still have a couple things to iron out in practice."
Kyle Lowry added 10 points for Toronto (17-31), while Aaron Grey had a game-high 12 rebounds to go with six points.
Dwyane Wade added 23 points for the Heat (30-14).
Raptors coach Dwane Casey knew the Heat would be hungry, coming off a 102-89 loss Friday in Indiana.
"They're going to be like a bunch of wet hens," Casey said before the game. "They're going to be really, really ready to play."
Toronto, meanwhile, was coming off a thrilling 98-73 victory over the Los Angeles Clippers in Gay's Raptors debut.
And while the Heat needed overtime to beat Toronto 123-116 when the teams met on Jan. 23 in Miami, that wasn't the case Sunday.
Toronto led by eight in the second quarter, but were trailing 71-67 by the end of the third, and six consecutive points by Bosh gave the Heat a six-point lead with 5:41 left.
"They're the defending champs," Gay said. "I say for three-and-a-half quarters we played them as well as anybody in the league. The fact that we haven't been together for a long time, they exposed that in the fourth and a little bit in the third."
A DeRozan dunk made it a three-point game with under five minutes to play. But a wide open Bosh drained a three-pointer from the corner, James followed it up with a dunk and then a three of his own to put the Heat up by 12 and the game out of reach with 1:28 left to the disappointment of an Air Canada Centre capacity crowd of 19,800.
Bosh's three prompted one fan to stand up and holler: "Why couldn't you play like that when you were in Toronto?"
"I'm a little surprised," Bosh said of the booing. "But, you know, they paid their money they can do what they want. I hope they just remember the good times."
DeRozan had high praise for his former teammate.
"I sat right next to (Bosh), his locker was right next to mine, just to play with an all-star like that my rookie year, the type of player he was, that helped me," DeRozan said. "Obviously he was the No. 1 option when he was here, but he's stepped into his new role (as part of a trio of stars).
"I think he was definitely a key component to win that championship that they won. He's just doing what he does, from rebounding, playing defence, to scoring the ball. Everybody knows he can score the ball when he wants, and he proved it tonight."
Toronto shot just 37 per cent on the night to the Heat's 53 per cent. The Raptors' bench was of little help to the starters, shooting just 4-for-18 for 11 points.
James had attended the Toronto Maple Leafs' 1-0 loss to Boston the previous night — he tweeted that it was the first time he'd seen an NHL game live. Pictures of James holding the Grey Cup at a local sportsbar, where he joined some Toronto Argonauts players, appeared on Twitter later in the night.
The Heat grabbed an early lead punctuated by a monstrous James dunk that put the visitors up by 10 points midway through the first quarter. The Raptors chipped away at the deficit, eventually trailing 24-21 head into the second.
Toronto opened the second with a 14-4 run to take a seven-point lead and would go up by eight before taking a 50-44 lead into the dressing room at the break.
Six turnovers proved costly in the third quarter. The Heat — Bosh leading the way with nine points — outscored Toronto 27-17 in the frame and led by four with a quarter left.
Notes: The game marked the 62nd time that James, Wade and Bosh combined for more than 70 points. . . The Raptors were missing Landry Fields (back spasms). ... The matchup was the second of a three-game homestand for Toronto. The Raptors host the Boston Celtics on Wednesday.