Lucas Raymond and Alex DeBrincat each had two assists for Detroit. Ville Husso made 15 saves before being replaced in the second period by Michael Hutchinson, who made 12 saves.
Dylan Strome and Matthew Phillips each had a goal and an assist for Washington. Hunter Shephard made 20 saves.
Austin Czarnik gave the Red Wings a 1-0 lead at 7:19 of the first period.
Moritz Seider scored a power-play goal to make it 2-0 at 13:12, and Larkin scored his own power-play goal to push it to 3-0 at 2:46 of the second period.
Strome cut it to 3-1 with a power-play goal at 8:48, but Cross Hanas responded for Detroit to make it 4-1 at 13:20.
Phillips finished off a tic-tac-toe passing play at 15:00 to make it 4-2.
Larkin scored his second of the game at 5:43 of the third period for the 5-2 final.
