Clark closed with a 5-under 65 at rainy Royal Montreal for his second PGA Tour victory. The 38-year-old South African player also won the 2010 Players Championship.
Furyk, the two-time Canadian Open champion who took a three-stroke lead into the final round, finished with a 69. The 44-year-old American matched Clark with a birdie on the par-3 17th and a par on the par-4 18th.
Clark had a 17-under 263 total.
Justin Hicks shot a 64 to finish third at 13 under.
