The 28-year old Tomasulo rallied on the final day, racing by the leaders to finish with a 24-under par total 261 at the Georgian Bay Club.
Bradley birdied the final hole for a 6-under 65 to finished in second. Kevin Chappell, who held a five-stroke lead after three days, managed even-par 71 to wind up at 22 under and in third place.
"To be honest, I thought he [Chappell] was uncatchable because of the way he played the first three rounds," said Tomasulo, who won for the second time in his career, both coming in Canada. "I thought we might be able to get something going and think about second place. I wasn't expecting to shoot 10 under."
Chappell was looking for his second win of the year.
"There wasn't much that was good," he said. "It was just sloppy all day. I never got into a rhythm. I was really searching on the back side to find it. I hit some good shots down the stretch and had a chance to catch Pete and I just couldn't do it. The putter let me down this weekend. It's disappointing."
Bradley, who started the day in second and five back of Chappell said Saturday that somebody could shoot 61 on Sunday, considering he'd done it on Friday and Chappell did it in Thursday's opener.
"I felt like I played great all week and I was close to a really good round," said Tomasulo, who also shot a second-round 61 in his first win in the 2005 Alberta Classic. "I just tried to stay patient. All of a sudden I started making putts and hitting it close today. I just got on a roll early and kept it going."