Maggert took the lead in the Charles Schwab Cup standings, 119 points ahead of Colin Montgomerie. Montgomerie skipped the tournament because of commitments in Europe.
Maggert finished at 14-under 202 at En-Joie Golf Club. He won the Regions Tradition in May and the U.S. Senior Open in July, both major championships, and took the Shaw Charity Classic three weeks ago in Canada.
The Texan's second straight 68 on Saturday put him in good position for another win, and he took advantage in a big way with six birdies in a bogey-free round.
Bernhard Langer, the winner last year and third in the Schwab Cup, failed to earn any points. He tied for 20th at 6 under after a 68.
The victory was worth $285,000 and boosted the 51-year-old Maggert's earnings for the year to $2,094,976.
Second-round leader Rod Spittle (74) of Canada, bidding for his second career victory, couldn't keep the magic going that had placed him atop the leaderboard after rounds of 68 and 66.
Fifty-year-old Scott McCarron (75), who had a 64 on the second round and was tied for second with John Huston to start the day, faltered in his fourth Champions Tour event. He made only two birdies and a triple-bogey 7 at the 15th hole put a damper on his day.
As usual, the ninth edition of this tournament came down to the closing holes. Trailing by one shot on a warm, humid afternoon, Goydos hit his tee shot into the large water hazard that lines the left side of the fairway at the difficult par-4 15th hole and had to take a penalty as Maggert paused to watch.
Goydos recovered to make bogey and lose just one shot, then missed a birdie putt inside 8 feet at No. 16 after driving over a cart path to the right of the green.
Pavin tied Goydos at 12 under with a brilliant pitch for birdie from off the fringe at the par-3 17th. Moments later, the smile on Pavin's face disappeared when he hit his tee shot into the water hazard at No. 18. He then walked the fairway with head down, frustrated at a lost opportunity.
Maggert stayed out of trouble over the final three holes and was home-free when Goydos missed a birdie putt at No. 18.
Huston, the winner here four years ago, was at 10 under heading to the par-3 seventh but took himself out of contention to become the tournament's first repeat champion with a triple bogey. He mis-hit his drive, the shot nearly landing in the imposing water hazard that guards the right side, had to take a penalty, and couldn't recover when his next shot landed in a greenside bunker.
Maggert, two shots behind Spittle at the start of play, birdied the first three holes to reach 11 under and added two more before the turn. He chipped to a foot at the par-5 eighth hole and rolled in a 10-foot putt at No. 9.
The surge continued at No. 10 when Maggert rolled in a 40-foot putt to reach 14 under, two shots clear of Goydos.
Goydos, who began the day tied for fourth with Maggert, Woosnam and Stephen Ames, also started with a flurry of five birdies on the front side, but he, too, faltered at No. 7, making bogey. A birdie at the par-5 12th had Goydos back within one of the lead at 13 under.