Pouliot's shot from the side of the net hit the post but bounced back into the net off Colorado forward Gabriel Bourque.
The winning goal was set up by 19-year-old rookie Elias Pettersson, who led the Canucks with two goals and three assists. Pettersson's second goal came in the final minute of regulation and forced overtime. The two-goal effort was his second of the week and third in nine career NHL contests.
The injury-riddled Canucks posted their third straight win, while the Avalanche suffered their third consecutive loss.
Brock Boeser also scored twice for the Canucks, and Loui Eriksson and Markus Granlund tallied the other Vancouver goals.
Boeser called the game a "blast" in a postgame interview with Sportsnet.
"It just shows the type of team we have and what we can do to battle back," said Boeser.
Nathan MacKinnon led the Avs with two goals and an assist, while Alex Kerfoot provided a goal and an assist. Sheldon Dries, Ian Cole and Nikita Zadorov were the other Colorado scorers. Mikko Rantanen added three helpers.
Boeser scored on a breakaway at the 58-second mark on the game's first shot. The goal came after Colorado's MacKinnon missed the net on a breakaway shortly following the opening faceoff.
Vancouver's 1-0 lead held up after 20 minutes, but the clubs erupted for seven goals in the second period and were tied 4-4 after 40 minutes.
Zadorov's first goal of the season lifted the Avs to a 5-4 lead only 1:30 into the third period. But Granlund created a 5-5 deadlock on a power play midway through the final frame. The Avs regained the lead on a power play as MacKinnon fired in a pass from Gabriel Landeskog, who had drawn a tripping penalty to Bo Horvat.
But Horvat atoned for his miscue by setting up Pettersson's second goal of the game with only 36 seconds left in regulation time while Markstrom was pulled for an extra attacker.
(This story has not been edited by Devdiscourse staff and is auto-generated from a syndicated feed.)