Kerr, who also won in 2005, went from one shot behind to the lead when Song-Hee Kim of South Korea made a double bogey on the par-4 16th and Kerr made her birdie moments later a hole behind.
Kerr held on for her 12th career victory and earned the $330,000 winners check, moving her to the top of the money list on the LPGA for the season with more than $700,000.
In-Kyung Kim finished second when Wright bogeyed the finishing hole.
Wright, who shared the third-round lead with Kerr, and Song-Hee Kim shared third at 271.
Lorena Ochoa, whose 13-under total after two rounds was a tournament record, started the day five shots back, and a birdie on the first hole hinted that she might make a charge.
But the worlds top-ranked player followed with bogeys on three of her next four holes and faded. After making the turn at 14 under Saturday, she was 7 over the rest of the way.
Kerr, meanwhile, was steady but not spectacular with two birdies and only one bogey in a 70. Of the four players in contention with four holes left, she was the only one to finish under par, and said her new attention to her mental focus paid off in the tense final holes.
I was surprised, she said behind the green at the 72nd hole after rolling in her short putt to clinch it. I was even calm at 18. I guess that mental training is paying off.
Only two holes earlier, Kerr had missed a makable par putt at the par-3 13th hole, and when Wright followed by also making bogey, there was suddenly a four-way tie for the lead.
As the tension mounted, so did the mistakes by the leaders, all of whom failed to post the low numbers that dominated the first three days despite a sun-splashed but breezy Sunday. Even the greens were again softened by an overnight thunderstorm, but few took advantage.
Only half of the top 10 finishers shot under par, and none was better than 3 under.
But it was Kerr, chirping at her ball in the air, who made the play of the day.
At No. 15, she was about 220 yards out and went for the green in two.
Come on, be right! Come on! she pleaded as she watched it soar toward the green, where it rolled on and then just over, leaving her with a puttable ball from the back fringe.
From there, a two-putt birdie was more than enough to carry her to her first victory of the year as her less-experienced challengers all failed to come up with the shot they needed.
A hole ahead, leader Song-Hee Kim was finishing off a double bogey after a pulled approach, a chip over the green and then two putts, and the her playing partner, In-Kyung Kim, watched all that, then missed her own par putt to fall two strokes off the pace.
Wright, a six-year tour member seeking her first victory, fell two back when she missed the green with her approach at the difficult par-4 16th, chipped on and two-putted.
Pars on the par-3 and par-4 finishing holes made Kerr the first two-time winner here since the LPGA event began seven years ago, and perhaps the only one. All week, the tournament was played under a cloud of doubt that the contract will be renewed for next year.