Watson had a share of the lead with Oklahoma native Gil Morgan entering the final round but enjoyed a bogey-free day and earned his first victory in 14 starts on the Senior Tour this season.
"I didn't make the mistakes that Gil did," said Watson, who had a weather-affected 72-hole total of 14-under 274. "And Gil, as a result, finished second."
Watson knows how it feels. He was a runner-up five times in his first 13 Senior Tour starts this season, either getting beat or beating himself with a shaky short game.
"I blame some of my second-place finishes on my putting woes," said Watson, who won this event two years ago in Myrtle Beach. "And I hope this, too, will pass some day. It may not. I may always have problems with my putting. I don't know."
Watson had some heartbreaking runner-up finishes this season. Of the five, two came by one stroke and two others in a playoff. But he said he's learned from them, even in the twilight of a Hall of Fame career.
"It's true in life, Bobby Jones said, that you don't learn by your victories, you learn in your failures," Watson said.
Morgan's failures were minimal this week, but his most costly came Sunday at the par-4 16th hole, which he bogeyed to fall two strokes off the pace, all but ending his chance at a second Senior Tour Championship title.
"Well, about 16, I slit my wrists," said Morgan, who won this tournament five years ago in Myrtle Beach for one of his 21 Senior Tour victories.
It was a two-man tournament. Bob Gilder, who shared the tour lead with Hale Irwin with four wins this season, was third at 9-under 279. Irwin was fourth at 281, good enough to become the first $3 million man in Senior Tour history.
"I'm glad it's over," said Irwin, who already had clinched the $1 million Charles Schwab Cup bonus. "It's been a wonderful year, but it's time to jump off and get a little R&R."
Scores were relatively high at Gaillardia, where temperatures over the first three days were in the 40s.