Gushue used the hammer to score two in the seventh to tie the match before stealing one in the eighth for the win.
He will face Saskatoon's Steve Laycock, who used the hammer in the eighth to beat Edmonton's Brendan Bottcher 6-5.
After Laycock scored three in the fifth to go up 5-2, Bottcher came back to score two in the sixth and one in the seventh to tie the game.
On the women's side, Ottawa's Rachel Homan and Scotland's Eve Muirhead will face each other in the championship game after semifinal wins.
Homan advanced after stealing one in the eighth end against Edmonton's Heather Nedohin en route to a 4-3 victory. Homan shot 94 per cent in the match while her third Emma Miskew was close behind, shooting 93 per cent.
After Homan scored singles in the third, fourth and fifth ends, Nedohin had singles of her own in the sixth and seventh ends to tie the game.
Muirhead scored four in the sixth end to defeat Edmonton's Val Sweeting 6-3. After trading points in the early going of the match, it was the big sixth end that was the difference.
Earlier in the day, Muirhead upset Sochi Olympic champion Jennifer Jones of Winnipeg 8-5. Muirhead broke a 5-5 tie in the eighth end by scoring three to secure the quarter-final victory.
Homan shot 98 per cent and scored three in the fifth end to beat Switzerland's Binia Feltscher in her quarter matchup.
Nedohin defeated fellow Edmonton native Chelsea Carey 9-3. Sweeting hung on to defeat Sherry Middaugh of Coldwater, Ont. 5-4 to advance.
In the men's quarters, Gushue scored three in the eighth to beat Olympic champion Brad Jacobs of Sault Ste. Marie, Ont. 7-5. Laycock used the hammer to score a single in the extra end and defeat Jim Cotter of Kelowna/Vernon, B.C., 6-5.
Koe had a huge seventh end by scoring five en route to a 7-2 win over Winnipeg's Reid Carruthers while Bottcher scored four in the sixth end to beat Winnipeg's Mike McEwen 6-3.