Kyle Thompson, who held a share of the lead after three rounds, posted a 4-under 68 to finish one shot off the lead at 22-under-par 266. Overnight co-leader Ryan Palmer was one shot further back at 21-under-par 267.
Bohn was in a tie for fourth to start the day at the Black Creek Club and birdied the par-4 first. He added a birdie at the fifth and another birdie at the ninth to make the turn at 18-under par.
'Chasing the leaders is a lot different,' said Bohn. 'You have to keep firing at flag sticks. I had to keep thinking birdies, which is easier to do that than trying to protect a lead by making pars.'
The 30-year-old caught fire on the inward half to take command of the tournament. Bohn ran off three consecutive birdies starting at the par-4 12th and reached minus-22 with a birdie at the 16th.
Bohn, who attended the University of Alabama, picked up a closing birdie at the par-5 18th to clinch the breakthrough victory, one that surpasses the thrill of shooting a 58 on the Canadian Tour and winning $1 million in a hole-in-one contest.
'This means so much more to me,' said Bohn, who collected $81,000 for the win. 'Making a hole-in-one and winning that money was pot luck. Shooting 58 was pretty special and one I'll never forget but this one is the result of a lot of hard work, both mentally and physically. It all paid off for me, way more than hitting one shot.'
Thompson, who was also seeking his first career victory on tour, had two bogeys and a birdie over his first nine holes. He birdied the 10th to return to 18-under and tallied an eagle at the par-5 14th.
The 24-year-old birdied two of his last four holes to come up one shot short.
'I didn't make anything most of the day,' said Thompson.
Palmer, who was seeking his second victory of 2003 after capturing the Clearwater Classic earlier in the year, had a bumpy front nine with three birdies and three bogeys.
The 26-year-old ran off three consecutive birdies from the 13th but it wasn't enough to overtake Bohn.
Jimmy Walker shot a 6-under 66 to join Tom Carter at 20-under-par 268.
Vaughn Taylor, who won the Knoxville Open in June, was one shot further back at 19-under-par 269 along with Lucas Glover, Ted Purdy, Rob Bradley and Bart Bryant, who closed with a 9-under 63 on Sunday.