"Yeah, it feels good to beat this team, but it always feels good to win in a building like this," Sanford said.
The 32-year-old goalie made 18 saves in his 10th straight start.
"He's a veteran player, a professional that has an opportunity sitting right in front of him here to take the ball and run with it. He's doing just that," Blue Jackets coach Scott Arniel said.
Gionta scored a goal with 1:21 left in regulation to send the game to overtime. The Montreal captain, who missed half of the second period after he was cut on the face by Blue Jackets defenseman Marc Methot's skate, tapped home a puck in the crease after Tomas Plekanec's centering pass struck former Canadiens defenseman James Wisniewski in front.
Andrei Kostitsyn scored with 1.5 seconds left in the first to draw Montreal even at 1.
Carey Price stopped 26 shots for the Canadiens, who returned home after a 1-1-1 West Coast trip.
"We haven't had consistency for a long time here," Gionta said. "It doesn't matter whether it's on the road or at home, we've got to find ways to bring the same effort. We know what wins us games, we just aren't doing it on a consistent basis."
Gionta was injured midway through the second. He went down on the ice after Methot's leg kicked up and struck him in the face after he checked him into the boards.
"We both kind of fell the opposite way of each other," said Gionta, who had words with the Columbus bench as he went to the dressing room at 11:07. "I haven't seen the play but I'm just lucky it caught me where it did."
The veteran right wing missed the rest of the period before returning for the start of the third with stitches in both his lips.
"It happened so fast and I was just focused on hitting him," said Methot, who wasn't aware of the accident until he saw a replay. "I thought it was clean but it could have been a freak accident, and it almost was, so I'm just grateful that my skate didn't go all the way up."
Prospal quieted the sold-out crowd just over 2 minutes in when he beat Price for his seventh goal.
Columbus held a 10-7 shots advantage in the first period, but Kostitsyn made the Canadiens' last one count. He drove in and snapped a shot past Sanford for his third goal in four games.
Umberger gave Columbus a 2-1 lead off the ensuing faceoff after Methot's hit on Gionta. He took defenseman Nikita Nikitin's lead pass and drove the left side to beat Price between the pads with a low wrist shot at 11:14.
Price stuck out his left pad to deny Umberger on a breakaway to keep it a one-goal game with less than a minute left in the second after Montreal defenseman P.K. Subban turned over the puck and fell inside the Blue Jackets' blue line.
Sanford's only other appearance against the Canadiens was with St. Louis on March 10, 2007. He was pulled after allowing three goals through the first 25:14 of Montreal's 4-3 road win. ... Pacioretty returned after serving a three-game suspension for his hit to the head on Pittsburgh D Kris Letang. ... RW Louis Leblanc, the No. 18 pick by Montreal in the 2009 draft, made his Bell Centre debut after playing his first three NHL games during the Canadiens' trip.