First, Brianne Jenner raced up the left wing and fired past American goalie Jessie Vetter with 3:26 left to play.
The Americans almost sealed the win when a shot from their end of the ice hit the post of a Canadian net left empty in favour of an extra attacker.
That proved costly as Poulin, 22, of Quebec City tied the game moments later, deflating an American team that could almost taste their first Olympic gold medal since 1998.
The quick-footed U.S team had taken a 2-0 lead earlier in the third period when U.S. rookie Alex Carpenter, daughter of former NHLer Bobby Carpenter, netted a wrist shot off a rebound.
American captain Meghan Duggan opened the scoring in the second period, ripping a high shot from the hashmark past Canadian goalie Shannon Szabados, who was screened by U.S. veteran Julie Chu.
It's Canada's fourth consecutive Olympic women’s ice hockey gold.
The win capped an undefeated run in Sochi for a Canadian team which has now won four of the five gold medals awarded since women’s hockey made its debut at the 1998 Nagano Winter Games.
Switzerland beat Sweden earlier on Thursday to claim bronze
Shannon Szabados made 27 saves in the Canadian net while Jessie Vetter stopped 28 shots for the U.S.
With the same two goaltenders in the nets, the Canadians beat the U.S. 2-0 four years ago in Vancouver.
Stephen Harper’s airborne plane erupted in cheers Thursday as the prime minister himself announced the women’s Olympic hockey victory over the United States.
As the Canadian delegation was winging its way home from a summit meeting in Mexico, Harper’s disembodied voice cracked over the plane’s public address system about 3 p.m. Eastern time.
Harper joked that he was taking over the plane and had a special announcement.
A hockey fan and author, the prime minister delivered the news of how the women’s team came from behind for a dramatic 3-2 overtime win over the U.S.
Loud cheers rang through the cabin.
Harper had wagered U.S. President Barack Obama a case of beer on the game; another one is on the line Friday as the Canadian men face their American counterparts in a semifinal matchup.
“It was a great victory,” Harper said. “President Obama, I’ll be looking forward to my beer.”
This post has been brought to you by Luongo almost having a heart attack
Seriously I think I'm having a legit panic attack #CANvsUSA— Strombone (@strombone1) February 20, 2014
CRYING CAUSE I SLEPT IN AND MISSED THE GAME! BUT I'M EXCITED CAUSE I'M GONNA GO WATCH THE OLYMPIC TORCH IN VANCOUVER BE LIT UP TONIGHT! I HOPE TEAM CANADA IS POPPING BOTTLES AND SMOKING CIGARS RIGHT NOW
~NEVA 4 GET 2010~