Plekanec scored a shorthanded goal on a two-man breakaway in the first period with Pacioretty, who had a goal and an assist in a 3-1 win against the New York Rangers at Bell Centre.
"They get chances and they defend well and they get the defense tricked, but I don't remember the last time they got a 2-on-0 on penalty killing," said Canadiens coach Michel Therrien, who coached his 600th NHL game.
Carey Price made 34 saves to help Montreal get off to its best start in 53 years.
Lars Eller scored his first goal of the season for the Canadiens, who swept their four-game homestand to improve to 7-1-0. That matched the team record for most wins through the first eight games of the season achieved twice before, including 1961-62, when they won seven and tied one.
Montreal also got off to a 7-1-0 start in 1924-25.
"I don't think we should put too much into it," Eller said. "It's not like we're the best Habs team in 50 years, but we do have a really good feeling within this room. It's a hungry group and at the same time it's a humble group, and the encouraging thing is that I think we're getting better and better. The four games we played at home here are probably the four best games we played this year, and there's still room for improvement, but things right now are looking very good."
"For me, the game was decided in front of the two nets," New York coach Alain Vigneault said. "They were stronger than us in front of ours and were able to score two goals where we lost the battles, and we weren't efficient enough in front of their net, which is to say we didn't get second chances in front of Price."
Price made a dazzling glove save on a shot by Derick Brassard in his first game against the Rangers since Game 1 of the Eastern Conference Final last spring. The Montreal goalie was sidelined for the rest of the series, which New York won in six games, after Price sustained a knee injury when Rangers forward Chris Kreider slid into him.
"I think that was an important game for our team," Price said. "Obviously we wanted to end our little homestand on a good note before we hit the road. So I thought we played pretty well overall. I was just trying to do my job and help the guys win."
In his past three starts, Price has allowed four goals and stopped 93 of 97 shots.
"He's playing like one of the top goalies in the League, and tonight was no different," Therrien said.
Eller put the Canadiens up 2-1 at 11:46 of the second when he put a loose puck under Lundqvist on a scramble in front of the net.
Pacioretty made it a two-goal margin with his third goal at 6:35 of the third.
The Rangers were caught up the ice on the power play when Plekanec scored his fifth goal to give the Canadiens a 1-0 lead at 12:06 of the first period.
With Montreal center Manny Malhotra in the penalty box, Plekanec chipped a puck off the boards past Rangers captain Ryan McDonagh in the Canadiens zone to send himself and Pacioretty in alone on Lundqvist. Plekanec passed the puck back and forth with Pacioretty, sending the Rangers goalie from side to side before shooting into the right side for his fifth goal.
"The timing of the passes worked out well that the last pass from [Pacioretty] came at the right time, like far away from the crease so he couldn't stop it and he still had to move side to side. We caught him pretty good," said Plekanec, who could not recall ever having had a similar opportunity.
It was the first time Montreal scored the first goal of the game since its season opener on Oct. 8, a 4-3 win at the Toronto Maple Leafs.
"When you're on the power play and you're looking to get the momentum and they get a goal like that, it's tough," Rangers right wing Martin St. Louis said.
The Rangers failed to convert both of their power-play opportunities and are now 2-for-22 this season. New York has allowed two shorthanded goals.
"It was very unfortunate with the power play when you don't get anything going there and we obviously give up one on the bad decision by myself," McDonagh said. "You can't allow yourself to start a game like that on the road. Two power plays and you don't generate much and you give up one."
The Canadiens had trailed in each of their first seven games. A brilliant stop by Price in the second helped them end that streak.
Hagelin scored his second goal in three games to draw the Rangers even at 17:07 of the first. Price got his glove on Dan Girardi's shot from the right point, but the puck popped out and Hagelin batted it out of the air and into the net from the right side of the crease.
Brassard came out of the penalty box in the second and created a scoring opportunity. The Rangers center fired a wrist shot targeted for the top right corner, but Price flashed his glove to keep the score tied 1-1.
"We're a confident hockey club," Price said. "We're enjoying coming to the rink. We enjoy putting the work in. We stick up for each other. We're not trying to do anything special. We're just having fun and trying to get the job done."
Montreal begins a three-game road trip Monday at the Edmonton Oilers; the Rangers open a four-game homestand Monday at Madison Square Garden against the Minnesota Wild.