Coming off a maiden win in his seventh start for owner Woodford Racing and trainer Mark Casse, Gallant was ridden to victory by Corey Fraser at odds of 15-1.
Gallant, who took the lead from the 7-5 choice Milwaukee Appealafter the opening quarter of a mile, battled the filly head-and-head along the inside down the homestretch, prevailing in a close photo.
Queen's Plate winner Eye of the Leopard closed for the show spot, a half-length back, meaning there will be no Canadian Triple Crown winner this year.
The winning time was 1:56.74 on a fast track for the 1 3/16-mile test.
Gallant, by Aptitude out of the Touch Gold mare Quintessa, was ridden by Fraser for the first time in the Prince of Wales. The gray/roan colt was making his first start away from Woodbine.
Milwaukee Appeal, ridden by Stewart Elliott, took the early lead while pressed by Gallant. After a slow opening quarter mile of :24.80, Gallant took over on the outside and proceeded to show the way through fractions of :49.10 and 1:12.94. Milwaukee Appeal closed to within a head and the pair threw down for the stretch run with Gallant winning in a thrilling finish.
Second choice Eye of the Leopard , always close to the leaders under Eurico de Silva, rallied on the far outside but could not reach even terms while continuing to gain as the trio hit the wire.
Winless in his first six starts, Gallant found the winner's circle when he came from far back to win by a nose over maidens May 31. His win in the Prince of Wales improved his record to 2-1-1 in eight tries with earnings of $347,267.
Robert J. Costigan bred the winner in Ontario.
Gallant paid $33.10, $11.10, and $3.60. Milwaukee Appeal, a narrowly beaten third in the Queen's Plate after a big win in the Woodbine Oaks prior to that, returned $3.60 and $2.30. The $2 exacta was worth $111.10. Eye of the Leopard was $2.40 to show.
The final leg of the Canadian Triple Crown is the Breeders' Stakes on the turf at Woodbine Aug. 2.