Alex Newhook scored the game-winner, his seventh of the playoffs, that sent the Sabres faithful into complete silence.
Montreal rookie goaltender Jakub Dobes recorded 37 saves, now winning back-to-back Game 7s these playoffs and having yet to lose two games in a row.
It's the Canadiens' first time advancing to the ECF since 2021, the same year they went on to lose in the Stanley Cup Final, and their fifth Game 7 overtime win, first since 1992.
It'll now be a showdown against the Carolina Hurricanes, who swept their way to the ECF, taking down the Senators and then the Philadelphia Flyers. Game 1 between them and the Canadiens is scheduled for Thursday, May 21st, which will have been 11 days of rest for the Canes.
Recap & Highlights
Phillip Danault recorded his first goal of the playoffs to put the Habs out in front 1-0 just 4:30 after puck drop. Kaiden Guhle (6) and Alexandre Texier (4) recorded the assists.
It was Montreal's eighth-straight postseason game with a goal in the first period, tying a franchise record (1993, 1978).
The game wouldn't see its first power play until almost 13 minutes in after Buffalo's Zach Benson got hit with a two-minute minor for delay of the game - the only penalty of the first period, a big step down from the seven in Game 6.
Montreal took advantage.
Zachary Bolduc scored his third goal of the playoffs to make it a 2-0 game, with assists from Nick Suzuki (9) and Lane Hutson (12). It marked Montreal's seventh power-play goal in their last 17 attempts.
Hutson became the fifth defenseman in Habs playoff history to record a six-game assist streak, joining Jacques Lemaire (1973), Larry Robinson (1978), Frank Mahovlich (1973), and Henri Richard (1960).
Meanwhile, Suzuki became just the second in Habs history (Mats Naslund, 1987) to record at least one point in eight-straight postseason games on the road.
Montreal led after the first period for the fourth time this series (Games 2, 4, 6) - they went 1-2 in those games. From the second period onwards in those three games, Buffalo outscored them 9-3.
The Habs went into this second period leading in shots (11-9), hits (14-7), and blocked shots (5-2).
Buffalo thought they might get their first power play of the game when a high-sticking penalty was called. But after further review, Zach Benson hit his own teammates in Josh Norris, drawing a bloody lip.
It would take a full 33:19 of game time before the Sabres finally found the net in the second period on their 15th shot on goal for the game.
Jordan Greenway scored his second goal of the playoffs to cut the lead in half, 2-1. The goal was originally credited to Mattias Samuelsson, who took the shot, but it bounced off Greenway.
Beck Malenstyn (2) and Jordan Greenway (2) picked up the assists.
Buffalo flipped the switch in the second period, entering the final frame with 58 shots (23 on goal) compared to Montreal's 30 (18 on goal). Neither team committed a penalty in the second, making it the fewest penalties in the first two periods between both teams in the series.
The Sabres had a chance at the start of the third period for their first power play of the game after Danault was called for a high-sticking on Samuelsson, but couldn't find the net.
But Buffalo preferred even strength.
Seven minutes into the third period, who else could it be but Rasmus Dahlin to tie things up 2-2 for the Sabres. Following the goal, the Sabres increased their shot total advantage to 70-38 over the Habs.
Dahlin scored his fourth goal of the playoffs, with assists from Owen Power (6) and Ryan McLeod (4), after coming off a historic five-point game.
His goal marked the 12th by a Sabres defenseman this postseason - the most by any team.
The game would enter overtime with only one penalty assessed to each team.
Buffalo had outshot 34-22 (SOG), while the Habs still kept the lead in both hits (24-19) and blocked shots (19-9). Montreal had only four shots on goal in the third period as the momentum completely swung in Buffalo's favor.
In the end, it was Montreal who emerged victorious.
