Mike Hoffman, Erik Karlsson and Mika Zibanejad scored first period goals for Ottawa, who out-shot the Toronto Maple Leafs 12-9 in the opening frame
Karlsson added his second of the night in the third period, the eventual game-winner, as the Senators handed the Leafs their sixth straight regulation loss.
The Leafs have scored just five goals in the six games.
“I scratch my head when I talk about that first period. That was totally done by ourselves, to ourselves, to a team that played last night,” said Leafs interim head coach, Peter Horachek. “It’s a strange situation. We’ve got to correct that for sure.”
Craig Anderson made 37 saves improving to 13-11-7 on the season.
David Clarkson snapped a 14-game drought scoring his first goal since Dec. 20 in the loss.
Nazem Kadri, who has reportedly begun contract talks with the Leafs, netted his 13th of the season while James van Riemsdyk had the other goal for Toronto.
James Reimer saw his record drop to 6-9-0 with a 22 save performance.
“We didn’t have a good start,” said Reimer. “Obviously you can’t get down 3-0 and expect to win in this league.”