Alfredsson scored a goal and added four assists as the Senators pounded the Canadiens 8-3 before a sold-out audience of 20,038 at Scotiabank Place.
Alfredsson led an offensive charge in which 11 different Ottawa players recorded at least a point, and the Senators (26-19-2) notched their fourth straight victory and fifth win in the past six contests.
"We clicked pretty good and made the most of our chances," said Alfredsson, who got off to a slow start this season but has since rebounded with 22 points in his last 13 games. "With the team having success, individual success comes with it."
Alfredsson and linemates Chris Kelly, who registered a goal and three assists, and Dany Heatley, who had a goal and two assists and also learned he would be off to Dallas to represent the Eastern Conference, combined for 12 points, spoiling the contest for several thousand Canadiens supporters who endured a long afternoon.
By the time this one was done, one large group of them sported paper bags on their heads in addition to their red, white and blue shirts.
The Senators scored four times in the first period and eventually chased Canadiens starting goaltender Cristobal Huet from the game as they halted Montreal's win streak at two games.
"The first couple of shifts were pretty good, then what happened after that ..." wondered Canadiens centre Saku Koivu. "There's no explanation or reason for that.
"It's not a slap in the face. It's a punch in the face."
Patrick Eaves and Mike Comrie each tallied once and set up another, while Wade Redden, Antoine Vermette and Andrej Meszaros rounded out the scoring for Ottawa.
Ray Emery, another player whom many believed was in the running for all-star honours, stopped 37 shots to earn the victory in goal.
"There are a lot of players on our team that could be deserving. It's nice, it's an honour to be picked," said Heatley, who will be joined at the all-star game by Montreal's Sheldon Souray, voted in as a starter on defence by the fans, and Huet, who was also added Saturday - the only highlight of a rough day for him.
Huet lasted less than half of the game, giving up six goals on 25 shots before being replaced by David Aebischer. Aebischer made seven stops the rest of the way.
"(Huet's) as deserving as anyone. He deserves any kind of recognition he's getting," said Souray, who had a power-play goal to set a franchise record for power-play markers in a season with 12, eclipsing a mark shared by Guy Lapointe, Mathieu Schneider and Patrice Brisebois.
Christopher Higgins and Craig Rivet had the other goals for the Canadiens (25-15-5), who have now lost four of six.
Otherwise, it was all Ottawa.
"It's hard enough for us to score goals right now," Souray said. "To give up goals like that, we're not going to come back."
Montreal had a 12-point lead in the standings over Ottawa on Dec. 23. But with a 9-1-1 record in their past 11 contests, the Senators have closed to a point in the hunt for second place in the Northeast Division.
"We gained some ground on them in the standings, it was a good game for us," Emery said.
The Canadiens have dropped six of nine contests and are 4-7 in that same 11-game span. Montreal completes its three-game road trip Monday night against the Detroit Red Wings.
"I don't think we've played our best in the last two or three weeks," Koivu said. "It's not going to get any easier. We've got to find a way to start winning again if we want to be one of the top teams."
Montreal applied the early pressure, forcing Emery to make a series of saves.
However, Redden snapped a shot over Huet's shoulder 4½ minutes in and that changed the momentum. Ottawa went on to fire a season-high 20 shots at the Montreal net in the first and, after Vermette made it 2-0 midway through, Comrie and Alfredsson scored power-play goals little more than two minutes apart to send the Senators to their dressing room with a 4-0 advantage.
With Montreal shorthanded early in the second, Higgins missed an open net on a 2-on-1 break and the Senators came right back down the ice and made it 5-0 on Heatley's rebound goal.
After Kelly made it 6-0 at 3:31, Huet was gone and the Canadiens responded with goals just 22 seconds apart, but the Senators scored twice more before the period was over.
Souray made it 8-3 with his power-play marker in the third.
The Canadiens went 1-for-6 with the man advantage; the Senators finished 3-for-5.
"We were a little excited today to play Montreal," Heatley said. "I thought it'd be a little tighter of a game than that."
Notes: - Eaves and Meszaros were named to play in the NHL YoungStars Game on Saturday. ... Ottawa defenceman Anton Volchenkov returned after missing Thursday's game with an ankle injury, but the Senators were still without centres Mike Fisher and Jason Spezza. ... Centres Steve Begin (back spasms) and Radek Bonk (neck) and defenceman Janne Niinimaa (flu) all sat out for Montreal, as did right-winger Aaron Downey, who was a healthy scratch. ... Ottawa plays host to Washington on Tuesday.