The Kraken retook a 2-1 lead before the first was over, as Brandon Tanev scored his team-leading fourth goal of the campaign.
That's how things stood after 20 minutes at a Climate Pledge Arena that featured some bleu-blanc-rouge in the crowd.
The Kraken extended their lead in the middle frame with a pair of goals 1:57 apart.
Yanni Gourde scored his first of the season to double the Seattle lead, before Tanev's second of the night made it 4-1.
The only goal in the third period was Ryan Donato's 5-1 tally at 5:14.
The Canadiens will be back in action on Thursday in San Jose, for the second stop of a four-game Pacific Division road trip.