McNulty ended the tournament at 16-under-par 200 for a one-stroke victory over Gil Morgan, who shot a 67 in his final round and had an eagle putt miss at 18 that would have sent things to a playoff.
Hale Irwin finished alone in third place at 14-under-par 202 after shooting a 68 on Sunday, while overnight leader Brad Bryant missed in his bid for a maiden Champions Tour victory with a 1-under 71 in his final round.
Bryant ended at 13-under-par 203 to take fourth place. Last week's winner at the Greater Hickory Classic, Jay Haas, finished one stroke further back in a tie for fifth place after a final-round 70. Joining him at minus-12 was Bruce Lietzke (67).
The 51-year-old McNulty carded two eagles on the day at Augusta Pines Golf Club. Beginning his round two strokes behind Bryant, he began making headway with his first eagle of the day at the par-5 second.
McNulty birdied No. 9 to make the turn at mius-13, but didn't really catch fire until after he stumbled to his only bogey of the day at 12.
On the next hole, McNulty rolled in a 40-foot eagle putt to reach 14 under. He followed that up with consecutive pars and a 15-foot birdie putt at the 16th to get to minus-15.
Then, after collecting another birdie at the last, McNulty watched as Morgan curled a long eagle putt past the cup at 18. If it had fallen, there would have been a playoff.
For McNulty, success at the end of the season has become a habit. He is the defending champion at the next two tour stops -- the SBC Championship and the Charles Schwab Cup Championship -- and he has six top-10 finishes in his last eight starts this year.
'You put a lot of things down to experience,' acknowledged McNulty, who collected $240,000 for the win. 'You hit the best shots you can, and I was fortunate to get two eagles today. I hit some nice shots when I had to.'
As for playing the back nine at 3-under-par to clinch the win, McNulty admitted it had something to do with a re-direction of his concentration after the turn.
'I was looking at the leaderboard and I said to myself 'I'm wasting energy looking at these leaderboards, just play,'' he said.
McNulty earned 240 Charles Schwab Cup points to move from sixth place into fourth place. Dana Quigley, who finished tied for 48th place at minus-1, still leads the season-long competition, but Irwin is within 261 points.
Irwin also moved closer to Quigley on the money list, but still trails by nearly $50,000.
Don Pooley, Bobby Wadkins and John Bland shared seventh place at 11-under-par after respective rounds of 67, 68 and 69. Bruce Fleisher (69) and Dave Barr (72) were one stroke further back in 10th.