Gerber made 33 saves, and the Senators won 4-1 in the season opener on Wednesday night.
Patrick Eaves, Chris Neil, Cristoph Schubert and Daniel Alfredsson scored for the Senators, who lost top players Zdeno Chara and Martin Havlat in the offseason. They didn't need them against the Maple Leafs, who have been outscored 44-20 in losing eight of nine games to Ottawa.
"Martin gave us a chance to win the game, especially early on," Alfredsson said.
Toronto had a few good chances but couldn't solve Gerber, signed in the offseason to replace Dominik Hasek.
Gerber won 38 games for Stanley Cup champion Carolina last season before losing his starting job to eventual Conn Smythe Trophy winner Cam Ward, his replacement in the Hurricanes' goal.
"You want to do well with your new team. Expectations are high. I'm pretty happy we got that win," Gerber said.
Ottawa coach Bryan Murray had Gerber in Anaheim and lobbied general manager John Muckler to get him when he was hired before last season.
"John knew I liked this guy. He did a heck of a job of staying on top of it until we got it done," Murray said.
Mats Sundin scored on a penalty shot for the Leafs, who are entering their 40th season since they last won the Stanley Cup.
The provincial rivals will meet again in Ottawa on Thursday night.
Before the game, the Maple Leafs honored former greats Borje Salming, Red Kelly and Hap Day by raising their numbers to the rafters.
Canadian Prime Minister Stephen Harper and Ontario premier Dalton McGuinty watched from the stands.
"When you have guys like Borje Salming on the ice before the game, if that doesn't get you going I don't know what does," Sundin said. "I don't care if you're 25 or 35, that's a great atmosphere."
Sundin said the game was closer than the score suggests.
"It's tough to lose the home opener, but I don't think it's as bad as the scoresheet says," Sundin said.
Ottawa jumped out to a 3-0 lead by the middle of the second period.
Neil made it 2-0 at 10:13 of the second by skating in on a 2-on-1 and putting a backhander over Raycroft's right shoulder before crashing into the net.
Schubert scored just over a minute later after he shot the puck in off Raycroft.
Just 30 seconds later, Ottawa's Anton Volchenkov took down Sundin on a breakaway -- causing a penalty shot. Sundin's shot trickled under Gerber and just past the goal line.
- Harper attended the game with his 10-year-old son Ben. Harper was booed when he was shown on the videoboard.
- Kelly cracked a joked in his speech before the game. "I never ever dreamed that I'd be hung from the top of a building," Kelly said.
- Preissing didn't return for the third period because of a lower body injury.