Miyazato finished 15-under 273, two strokes better than Stacy Lewis in taking her first victory in nearly a year and her first since the 2010 Safeway Classic.
The former world No. 1, who didn't crack this year's Top 10 until two weeks ago, led from start to finish in Sunday's final round, carding four birdies and two bogeys at Evian Masters Golf Club.
Lewis pulled to within one stroke thanks to a 15th-hole birdie but then stumbled to a bogey on the next hole, ending with a 2-under 70 to finish at 13-under 275. Still, it was her best finish since winning the Kraft Nabisco Championship earlier this year.
Knotted for third at minus-12 were I.K. Kim (70), Angela Stanford (71) and Miki Saiki (71).