Giroux was tripped by Pittsburgh defenseman Erik Karlsson while driving to the crease and fell hard into the right post, lifting the net off its moorings. Karlsson was initially called for a penalty, but after a review, it was determined the puck had already fully crossed the goal line before the net came off.
The Penguins then were unsuccessful on a challenge for goalie interference.
Tim Stutzle had a goal and an assist, and Drake Batherson had two assists for the Senators (27-21-7), who have outscored their opponents 19-6 in four straight wins. Linus Ullmark made 14 saves.
Egor Chinakhov had a goal and an assist, and Arturs Silovs made 28 saves for the Penguins (28-15-11), who have had two winning streaks end at six games in the past 36 days. They also won six in a row from Dec. 28-Jan. 8.
Chinakhov gave Pittsburgh a lead 1-0 at 7:57 of the first period. He took a pass from Evgeni Malkin for a wrist shot in the slot, his 10th goal this season and seventh in 16 games since being acquired in a trade from the Columbus Blue Jackets on Dec. 29.
Michael Amadio tied it 1-1 at 1:35 of the second period, stealing the puck from Malkin for a wrist shot from the slot that ended his 24-game goal drought since Dec. 13.
The Penguins were outshot 9-3 in the second and went 17:03 without a shot on goal until Chinakhov recorded one at 10:42.
Stutzle scored in a third straight game to put Ottawa ahead 2-1 at 6:46 of the third period. He scored his 26th goal this season, and fourth in five games, with a backhand on a rebound after Batherson had a shot on a breakaway turned away by a glove save from Silovs.
Novak then tapped in a rebound in the crease off a shot from Ryan Shea, tying it 2-2 at 8:48.
