Trouba completed the comeback with a shot from the point that went off Jeff Petry and in with 7:50 left in the game.
Backup goalie Alexandar Georgiev stopped 38 of 43 shots in the second game in two nights for New York following a 4-1 loss in Ottawa on Friday.
Max Domi and Artturi Lehkonen each scored twice and Shea Weber added another for the Canadiens (11-7-5), who have lost a season-high four games in a row. Nick Suzuki and Ben Chiarot had two assists apiece. Carey Price stopped 28 of 34 shots in taking the loss.
The Rangers trailed 5-3 in the third period before scoring three straight times.
Panarin scored at 5:51 on a no-look backhand pass from Chris Kreider, just 31 seconds after Lehkonen beat Georgiev from the slot for his second of the night.
Lemieux tied the game at 5-5 with a short-handed goal at 8:41 on a 2-on-1 break with Brett Howden.
Domi, back at center after playing the previous three games on the wing, snapped a nine-game goalless drought 2:03 in from the edge of the crease.
Montreal went up 2-0 halfway through the period when Lehkonen scored on a shot past the far post on Georgiev while using Trouba as a screen.
Domi made it 3-0 when he caught Georgiev off-guard with quick shot 34 with seconds left in the period.
Georgiev got a piece of Weber's slap shot at 2:51 of the second, but the puck still trickled in behind him.
The Rangers rebounded quickly, scoring three times against Price in a 3:20 span in the second. Chytil scored the first on a one-timer at 6:11 on a pass from Panarin. Buchnevich, playing his 200th NHL game, made it 4-2 at 7:06 when his shot went off defenseman Cale Fleury and in for his fourth of the year.
Panarin has at least one point in 13 of his last 14 games. . It was the first of three meetings between New York and Montreal this season. ... Montreal lost in regulation for the first time this season when leading after the first period (6-1-1).
Rangers: Host Minnesota on Monday night.
Canadiens: Host the Boston Bruins on Tuesday night.
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