Kyle Burroughs and Ilya Mikheyev also scored for the Canucks, and Thatcher Demko made 32 saves.
''It's a big one,'' Demko said ''That's one of the ones that we probably haven't gotten yet this year where, you know, we maybe did some things wrong but stuck together as a group and found a way to win.''
Luke Kunin scored twice, and Logan Couture also connected for San Jose. Kaapo Kahkonen stopped 16 shots for the Sharks.
''Obviously, very frustrating not to win this game. Totally winnable game for us,'' Kahkonen said.
Kunin forced overtime, tying it off a pass from Erik Karlsson with 5:15 to go.
''That was courage and character,'' Canucks coach Bruce Boudreau said. ''I mean, you know, we were obviously tired. We were obviously getting outplayed in the third period. But, you know, we found ways to bounce back twice was great.''
Couture gave the Sharks a 2-1 lead on a power play at 7:05 of the third period, scoring his 12th of the season. Mikheyev tied it 1:09 later, and Pettersson put the Canucks up 3-2 on a tip-in with 9:16 left.
''I liked the tempo, for the most part, all night long,'' Sharks coach David Quinn said. ''Listen, that's a good hockey team. I know what their record is but look at that lineup. They've got a lot of good hockey players.''
Canucks: Host Washington on Tuesday night.
Sharks: At Montreal on Tuesday night.
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