Jeff O'Neill and Mats Sundin scored in regulation for the Leafs (26-21-6) who remained in the thick of the Eastern Conference playoff hunt. Andrew Raycroft stopped 30 shots.
Daniel Alfredsson and Mike Comrie scored for the Senators (30-22-2) as Ray Emery faced 38 shots in a solid outing.
Emery and Raycroft were both solid in a scoreless first period, stopping several good chances to the delight of the 20,112 on hand at Scotiabank Place. Emery made a great save on Alexei Ponikarovsky at the eight-minute mark, while Raycroft looked stellar with a glove save on Mike Comrie late in the period.
Toronto outshot the Senators 18-8 in the second period and spent much of the period in the Senators zone.
The pressure paid off at the six-minute mark of the second as Matt Stajan found a wide open O'Neill, who beat Emery for his 18th goal of the season.
Sundin made it 2-0 with just over five minutes remaining in the period with a shot to the left corner.
Sens captain Alfredsson got his team on the board at 4:47 of the third period when he was left all alone and beat Raycroft to the left side.
Ottawa appeared to tie the game 12 seconds later on a goal by Mike Fisher, but the puck never crossed the goal-line.
Comrie tied the game at 8:06 of the third taking a great pass from Joe Corvo. Raycroft appeared to have made the save, but the puck trickled through his legs over the goal-line.
Ottawa was 1-for-4 with the man advantage. The Leafs were 0-for-2.
The Senators still hold a 4-2 edge over the Leafs in the season series.
Notes: Ottawa's RW Brian McGrattan and RW Denis Hamel were healthy scratchesaThe Leafs
were without C Mike Peca (knee, season), C Boyd Devereaux (ankle, day-to-day), C Darcy Tucker (foot, indefinite), C Kyle Wellwood (sports hernia, indefinite), D Andy Wozniewski (shoulder, indefinite), D Brendan Bell was a healthy scratch.