Adrian Kempe and Alex Turcotte each had a goal and an assist, and Vladislav Gavrikov and Kevin Fiala each had two assists for the Kings (48-24-9), who have won four straight and eight of their past nine.
David Rittich made 29 saves and stopped Chandler Stephenson on a penalty shot in the first period.
Los Angeles, which has clinched the No. 2 seed from the Pacific Division, will have home-ice advantage in the Western Conference First Round against the Edmonton Oilers, who will finish as the No. 3 seed from the Pacific.
Tye Kartye, Brandon Montour, Jaden Schwartz, Matty Beniers and Eeli Tolvanen scored for the Kraken (35-41-6), who closed their season with three losses in their final four games. Joey Daccord made 18 saves.
Helenius made it 1-0 at 15:14 of the first period, redirecting Gavrikov’s shot-pass over Daccord’s left shoulder.
Turcotte pushed it to 2-0 with a power-play goal at 16:23, deflecting Kempe’s feed through the seam in to an open net behind Daccord.
Kartye cut it to 2-1, scoring on a short-handed breakaway at 5:26 of the second period after he tipped a loose puck past Kempe at the Seattle blue line.
Montour tied it 2-2 with a power-play goal at 13:24, one-timing a Stephenson feed from the point through traffic and over Rittich’s glove.
Warren Foegele gave the Kings a 3-2 lead at 16:05, walking into the crease from below the goal line and wrapping a backhand around Daccord and past his left pad.
Alex Laferriere extended the lead to 4-2 at 17:17, finding Kevin Fiala’s rebound after a 2-on-1 rush. Fiala cut to the net and got stopped by Daccord, but Laferriere lifted it over his outstretched pad.
Kempe slapped Turcotte’s feed into an open net at 1:41 of the third period to make it 5-2, and Helenius scored his second of the game 57 seconds later to make it 6-2, swatting Jacob Moverare’s rebound over Daccord’s right pad.
Schwartz got Seattle back within 6-3 at 5:12, one-timing Jamie Oleksiak’s low-to-high pass over Rittich’s blocker from the left circle, and Beniers cut the deficit to 6-4 with a power-play goal at 13:34 by tapping Jordan Eberle’s cross-crease pass over Rittich’s glove.
With Daccord off for an extra attacker, Tolvanen scored a power-play goal with 28 seconds left, one-timing Shane Wright’s feed from the left circle over Rittich’s glove for the 6-5 final.
