Viktor Arvidsson, Pavel Zacha, Tanner Jeannot and Marat Khusnutdinov also scored for the Bruins (32-20-3), who are 10-1-1 in their past 12 games. Jeremy Swayman made 33 saves.
Boston's next game will be against the Tampa Bay Lightning in the 2026 Navy Federal Credit Union Stadium Series at Raymond James Stadium in Tampa on Sunday.
Travis Konecny had a goal and an assist, and Nikita Grebenkin and Matvei Michkov scored for the Flyers (24-20-9), who have lost three in a row, including 5-3 at the Columbus Blue Jackets on Wednesday, and 10 of their past 12 (2-8-2).
Samuel Ersson allowed five goals on 20 shots before leaving the game after the second period with a lower-body injury. Dan Vladar stopped all six shots he faced in the third.
Arvidsson gave the Bruins a 1-0 lead at 9:49 of the first period. He received a pass from Mittelstadt and scored five-hole on a one-timer from the right circle.
Zacha quickly extended the lead to 2-0 at 10:30. Morgan Geekie threaded a centering pass through two Flyers defenders to a cutting Zacha, who lifted a shot over Ersson's glove from the low slot.
However, Zacha left the game with an upper-body injury at 13:05 of the second period and did not return.
The Flyers thought they cut the lead at 12:03 of the first, but Christian Dvorak’s goal was overturned after the Bruins successfully challenged for goaltender interference.
Minten then made it 3-0 at 2:27 of the second period. Mittelstadt made a nifty move to avoid a defender in the neutral zone before sending a backhand pass to Minten, who skated in from the blue line and beat Ersson five-hole with a wrist shot from low in the left circle.
Konecny responded 49 seconds later to make it 3-1. Sean Kuraly turned the puck over into the middle of the ice, where Konecny was all alone to receive it and beat Swayman with a wrist shot glove side.
Mittelstadt pushed the lead to 4-1 at 16:12. Ersson got across to rob Andrew Peeke's backdoor tap-in with his left pad, but Mittelstadt was in position to collect the rebound and score with his backhand.
Jeannot made it 5-1 at 18:40 when he redirected Peeke’s slap shot from the right point.
Grebenkin cut it to 5-2 just 25 seconds later. Swayman stopped Konecny twice on a breakaway, but Grebenkin skated into the rebound and scored on the third opportunity.
Khusnutdinov scored an empty-net goal at 16:30 of the third period to make it 6-2 before Michkov scored a power-play goal at 18:19 for the 6-3 final.
