Andrei Kostitsyn scored with 5:11 remaining and Montreal recovered from blowing a three-goal lead earlier in the third period to beat Atlanta 5-4 on Tuesday.
Kostitsyn, who scored against Thrashers goalie Johan Hedberg to make it 4-3, helped set up two of the Canadiens' first three goals as Montreal carried a 3-0 lead into the third period.
Ron Hainsey scored twice as Atlanta netted three goals in less than a minute to erase their 3-0 deficit 7:27 into the third.
"After the game, I was happy," Canadiens coach Guy Carbonneau said. "I wasn't too happy after that minute. We had a brain cramp."
The Thrashers broke two franchise records for fastest goals. They scored three times within 59 seconds, including two seven seconds apart by Hainsey and Chris Thorburn.
"It wasn't like they were charging to get the fourth one, so sometimes when a team gets up 3-0 you're able to get some stuff going if they're sitting back a little bit, and I think that's just what happened," Hainsey said. "We just got a little momentum, got a power play, got a little more momentum and then it seemed like it was kind of even and they started skating a little more when it got to 3-3."
Hainsey, a former first-round pick of the Canadiens, drew Atlanta within 3-1 when he drove a slap shot past Carey Price from the top of the slot at 6:28.
He got credit for his second straight goal -- fifth of the season -- on a power play 52 seconds later. It stood up to a lengthy video review supporting referee Tim Peel's ruling that Price failed to stop the loose puck with his glove.
The Thrashers struck again after the ensuing faceoff when Thorburn took Marty Reasoner's pass and beat Price with a shot from the right side.
"When you get three goals scored against you that quickly when you're up 3-0, you kind of wonder what just happened there," Canadiens captain Saku Koivu said. "Obviously, we're going to review what happened and the mistakes that we made, but at the same time I think the way that we responded after those three goals was very positive."
Atlanta coach John Anderson felt it was a crushing defeat for his players, considering the comeback.
"It just breaks your heart, more than anything," Anderson said. "It's hard on the team."
The Thrashers have lost four in a row (0-3-1), and six of seven.
Matt D'Agostini scored his first NHL goal in the first period and Price stopped 22 shots.
D'Agostini, who played his second straight game since being recalled from Hamilton of the AHL on Friday, put a rebound of Kostitsyn's shot past Hedberg from the right edge of the crease 16:21 in.
"There's no point in celebrating your first goal with a loss," said D'Agostini, who played one game with Montreal last season. "The boys battled hard at the end and we got the two points. It wasn't a perfect game, but we'll take it and move on to Thursday."
Plekanec scored his sixth goal 14:22 into the second to put the Canadiens ahead 2-0.
Markov made it a three-goal lead with a power-play goal at 19:04.
- A moment of silence was observed in memory of former NHL All-Star Hubert 'Pit' Martin. Martin's body was recovered from Lake Kanasuta near his home in northwestern Quebec on Tuesday, two days after the snowmobile he was riding plunged through ice that cracked on the lake's surface.
- The Thrashers' previous record for fastest two goals was 10 seconds, set by Andrew Brunette and Matt Johnson on Nov. 17, 1999. The previous team record for the fastest three goals was 1:53, set by Shean Donovan, Steve Staios and Nelson Emerson on Dec. 26, 1999.
- Canadiens D Ryan O'Byrne, LW Sergei Kostitsyn and RW Guillaume Latendresse were healthy scratches.