Ehlers got a hold of a loose puck and cut across the top of the faceoff circle before button hooking at the hash marks and found DeMelo, who moved in and fired a wrister past Joey Daccord, beating him high glove side to seal the win for the Jets.
The win was their third straight.
It was also the 600th NHL career game for the Jet defenceman.
Mark Scheifele scored the other goal for the Jets.
Connor Hellebuyck made 18 saves for Winnipeg, who moved to 21-12-3.
Matty Beniers scored for the Kraken, who finished off a five-game road trip with a loss.
Joey Daccord turned aside 34 shots for Seattle, who dropped to 19-24-3.>[> Matty Beniers gave the Kraken 1-0 lead 8:12 into the first period when he jammed a Kappo Kakko backhand feed just under the cross bar.
Mark Scheifele tied the contest 9:35 into the second period on the power play when Kraken goaltender Joey Daccord kicked a rebound off a Kyle Connor shot right to Scheifele, who was parked inside the faceoff circle.
The Jet centre made no mistake, one timing a slap shot past him to score his 27th of the season.
Dylan DeMelo netted the game winner late in the third period to seal the win for the Jets.
Winnipeg wraps up an eight-game homestand Saturday when they face Calgary while Seattle returns home to host Los Angeles.
SHOTS-SEATTLE 19 WINNIPEG 36
ATTENDANCE-13,959
