Matt Duchene and Mikael Granlund also scored, and Esa Lindell and Mason Marchment each had two assists for the Stars (49-21-4), who defeated the Kraken 5-1 on Saturday. Casey DeSmith made 36 saves.
Dallas moved within four points of the Winnipeg Jets for first place in the Central Division
Kaapo Kakko scored for the Kraken (31-38-6), who are 1-4-1 in their past six and have been eliminated from playoff contention. Philipp Grubauer made 28 saves.
Kakko gave Seattle a 1-0 lead at 1:02 of the first period. He found Jaden Schwartz, who looped around the net before returning the pass to Kakko crashing the net for a one-timer in front.
Duchene tied it 1-1 at 2:34 of the first, redirecting Marchment’s wrist shot from the right circle under Grubauer’s blocker.
Johnston gave Dallas a 2-1 lead 45 seconds later at 3:19, tipping Lindell’s stretch pass by Seattle defenseman Vince Dunn to create a partial breakaway and snapping it past Grubauer’s blocker.
Granlund added an empty-net goal at 18:53 of the third period for the 3-1 final.