"There was no smiling and joking in this locker room after that game," Mavericks guard Jason Terry said. "That was embarrassing."
Jose Calderon had 15 points and Jarrett Jack scored 11 for the Raptors, who took the lead early in the second and never trailed again, leading by as many as 26. Toronto won for the seventh time in eight home games, reaching the midpoint of its season at 21-20.
"To get to where we want to go we're going to have to win big games and today was a big game," Bosh said. "We came out prepared and I'm really proud of my guys for the way they played."
It was Toronto's greatest margin of victory against Dallas, topping a 17-point win in 2001, and just the second win over the Mavericks in the past 12 meetings.
Dirk Nowitzki scored 19 points and Terry had 18 for the Mavericks, who have lost three of four. Shawn Marion scored 15 and Jason Kidd had 12 points and nine assists.
Toronto missed 12 of its first 15 shots and trailed 23-20 after one, but took command with an impressive second, making 15 of 23 field-goal attempts and outscoring Dallas 34-18. Bosh had 11 points in the quarter, and Calderon had nine points and six assists.
"The second quarter was our undoing," Mavericks coach Rick Carlisle said. "Turnovers led to uncontested shots and we went through a drought. When you go through a drought, you've got to stop them. We didn't do it and the end result is a loss."
Bosh said defensive energy keyed Toronto's second-quarter surge.
"Our defense initiated pretty much everything," he said. "We did a good job of playing defense and we pushed the ball when we had it. That got the momentum going."
Terry suggested Dallas' second unit may have overlooked the Raptors.
"I don't care who you're playing or what their record is," said Terry, a reserve. "When you're in their building, you've got to come out ready to fight.
"We come in the game and we just think it's going to be easy," he added. "Their second group came out there full of energy, making shot after shot, making plays. We didn't bring it."
The Mavericks showed their frustration as Toronto pulled away. Nowitzki received a technical foul for arguing a charging call in the third and Terry got one for arguing in the fourth.
It was Dallas' worst loss since a 131-96 setback at the Los Angeles Lakers on Jan. 3. There's little time to fix the problems; the Mavericks face the Celtics in Boston on Monday night.
"We've got to get out of here, we'll look at some of the problems that we had," Carlisle said. "We don't have a big turnaround time. We've got to get ready to play Boston."
Bargnani scored 11 in the third, including a pair of 3-pointers, as the Raptors carried an 84-68 lead into the fourth.
"He's way more athletic than I ever was," Nowitzki said of Bargnani, his fellow 7-footer. "He's shooting way quicker, he's got a quick first step. He's a tough matchup because he's so quick now off the dribble and he's shooting the ball really well this year."