Watney, who finished 127th this season on the PGA Tour money list, had an 18-under 270 total and earned $60,000.
'I've been working on my swing a lot and coming down the stretch I made some good shots,' said Watney, who parred the final three holes. 'It's definitely encouraging. I made some good putts and I played very well this week.'
Tomasulo, a former University of California star, also closed with a 68. He bogeyed the 15th to fall to 16 under, but birdied the 18th to pull within one.
Watney began the final round with a one-stroke lead after overcoming an eight-stroke deficit Saturday with a course-record 11-under 61 at Del Monte Golf Course. The 61 was best score ever posted in a pro tournament on the historic Monterey Peninsula.
Watney, who won a Canadian Tour event in 2003 and the Nationwide Tour Championship in 2004, will begin play Nov. 30 in the PGA Tour's qualifying tournament in Orlando, Fla., with hopes of regaining full tour status.
D.A. Points (69) and Charley Hoffman (66) finished two strokes back, and Parker McLachlin (69) followed at 15 under. First-round leader Tom Purtzer (71), Jim Thorpe (70) and Hunter Haas (71) were 14 under, with Thorpe and Purtzer topping the six Champions Tour entrants. Janice Moodie (69) paced the LPGA Tour players for the third straight year, finishing at 8 under.