Alex Newhook scored, and Nathan MacKinnon had the only goal in the shootout for Colorado (25-17-3), which has won five in a row, including 4-1 at the Vancouver Canucks on Friday.
"Hard checking both ways," Avalanche forward Mikko Rantanen said. "Both 'D' were defending well, not a lot of chances out there, and that's pretty much what playoff games look like. Came through even though it was a second game with a back to back, so really big one."
Ryan Donato scored for Seattle (27-14-5), which has lost three of four. Philipp Grubauer made 26 saves.
"It was a battle. We were in a battle for 65-plus minutes with the shootout," Kraken coach Dave Hakstol said. "Obviously, it's disappointing when you don't win in the shootout and get the extra point. In terms of our effort, our work level with battle was good throughout the hockey game. You'd like to be able to execute a little better in a couple of situations, but hey, it was that type of hockey game all the way through."