Pettersson scored two goals and had three assists as he was recorded for the fourth time with five points in an NHL game.
Pettersson carried Vancouver and was of course named player of the match.
With 1.47 left in regulation time, Vancouver picked off goaltender Spencer Martin and went for the equalizer.
Pettersson was lined up at the right drawing circle and after a couple of attempts he went down on his knees in a perfectly timed move and pulled in the puck that came parallel from the other side to make it 5-5 with 1.20 left.
Three frame hits by Vancouver in overtime
With 40 seconds left, Seattle came close to fighting back, but Justin Schultz's shot hit the post.
In overtime, Vancouver buzzed in front of Seattle's goal and was noted for a short period of time for two post shots and a crossbar shot, the latter by a red-hot Pettersson.
Petterson took the third penalty and chipped it under the shin pads of Martin Jones to make it 6-5 for Vancouver after the decisive penalty.
Petterson has been ill and missed three games.
He wasn't particularly keen to talk about it.
- It doesn't matter what illness I had and there are bigger problems in the world than me coming back to play a hockey game, Pettersson says to Vancouver's website.