Tuukka Rask, acquired from Toronto for Andrew Raycroft in 2006, earned the win.
"That was our type of hockey defensively, and for the most part offensively, too," Rask said.
Phil Kessel came into the game in search of his first goal — and 100th with Toronto — despite leading the Maple Leafs with 33 shots in the seven previous games. He has four assists.
Kessel's first drive came midway through the second period and glanced off the crossbar.
A Toronto goal was called off at 11:32 for goalie interference. Rask seemed to come out of his crease and run into Nazem Kadri as he tried to stop Cody Franson's shot from the point. Carlyle was incensed by the call after watching the replay on the big screen.
Boston won 17 of 21 faceoffs in the first period.
The Bruins had a goal disallowed at 6:30 of the second when the puck appeared to deflect off Seguin's skate past a prone Reimer. The NHL said the referee was in the process of calling the play dead before the puck went in, because of incidental contact between Boston's Brad Marchand and Reimer.
Marchand ended up crashing into the end boards on the play and went to the dressing room. He didn't finish the game.
Reimer was sharp in the second, when Boston outshot Toronto 12-6. Rask was also up to the task, stopping Kessel from close range with five minutes remaining.
The Bruins, killing off a slashing penalty to Seguin, hit the post with the Maple Leafs net empty with a minute remaining.
The Bruins were coming off their first regulation loss of the season, a 7-4 defeat against Buffalo on Thursday. They had given up only 12 goals in their previous six games.
Toronto had won two straight.
NOTES: Miami Heat star LeBron Jones, who was in attendance, tweeted: "At my first hockey game. Pretty Damn cool." James will be back in the arena on Sunday to play the Raptors. ... This was Boston's third away game in eight contests. They will wrap up their two-game trip to Canada on Wednesday at Montreal. ... Toronto will concludes its three-game homestand on Monday against Carolina. ... Jamie Tardif, called up from the Providence Bruins, made his NHL debut at 28 in his seventh pro season. Tardif, who has played 449 games in the ECHL and AHL since turning pro in 2006-07, led the Bruins out for warmups.