The singer's record Metals was nominated for the best Canadian album award along with Drake's Take Care, but she came out on top when rockers Arcade Fire announced the results at a gala in Toronto (24Sep12) on Monday night.
Feist gave a modest speech as she picked up the trophy, insisting she is a big fan of all the other performers who were nominated.
She told the audience at the city's Masonic Temple, "Everyone had a favourite record and I did, too, and I didn't think (the winner) was me... I'll be going to all these gigs, because I'd like to see an hour and a half of all these performers."
The singer also admitted she didn't prepare a speech and was left to ad-lib on the podium: "This is my worst nightmare. You'd think after a lifetime of terrible speeches that, at one point, I would think to write something down. But I never do because it seems presumptuous."
Feist previously missed out on winning the prestigious music prize in 2007 when her hit album The Reminder lost to Patrick Watson's Close to Paradise.
Arcade Fire won last year's (11) Polaris Music Prize for their album The Suburbs.