A shot by Bruins forward Elias Lindholm was stopped by Senators goalie Linus Ullmark, leading to a 2-on-1 rush the other way for Ottawa, which Tkachuk shut down.

Tkachuk also had an assist and Josh Norris and Michael Amadio scored. Ullmark made 14 saves for Ottawa (7-7-0), which has won three of its past six games (3-3-0).

It was Ullmark’s first time facing Boston after spending three seasons there from 2021 to 2024. The Bruins traded Ullmark to Ottawa on June 24 in exchange for goaltender Joonas Korpisalo, forward Mark Kastelic and a first-round pick in the 2024 NHL Draft, which they used to select Dean Letourneau (No. 25).

Pavel Zacha and Brad Marchand scored, and Jeremy Swayman made 31 saves for Boston (7-7-2), which has lost two of its last three (1-1-1).

Norris gave the Senators a 1-0 lead with 7.8 seconds left in the first period by sneaking a one-timer under the crossbar on the power play.

Zacha made it 1-1 at 4:51 of the second period with a spinning backhand shot after Nikita Zadorov kept the puck alive in the offensive zone.

Marchand gave the Bruins a 2-1 lead 15 seconds later, lifting a cross-crease feed from Justin Brazeau.

Amadio tied the score at 2-2 at 17:16 of the second, skating in and firing a shot past Swayman from behind the right circle.

Senators defenseman Travis Hamonic left at 4:11 of the third period after taking a shot from his arm.

Ottawa outscored Boston 12-0 in the third period.