McCullough carded three consecutive 4-under-par 68s to win the Mexico Senior Classic by one shot over Jim Colbert and Bob Eastwood at the La Vista Country Club in Puebla, Mexico.
Colbert and Eastwood shared the lead at 12-under through 16 holes, but both men bogeyed the par-3 17th, while McCullough recorded a birdie. All three men parred the final hole. Colbert had a seven-foot birdie putt to force a playoff, but missed right.
'I made key putts when I had to,' McCullough said. 'I've been working hard on my game lately. I've been close a couple of times.'
McCullough's victory comes in his Senior -Tour record 151st consecutive start in which he's been eligible. The 55-year-old's previous best finish was second in the 1998 Southwestern Bell Dominion.
He collects the $225,000 first-place prize, and moves from 29th to third on the 2001 money list.
Click here for Full-Field scores from the Mexico Senior Classic!