In a day that saw America sparkle, Stacy Lewis also wrapped up the Player of the Year award, becoming the first American to win it since Beth Daniel in 1994.
Kerr crucially parred the final three holes to hold off both second-round leader Inbee Park and Angela Stanford in the 36-player invitational.
"Coming in those last couple of holes it didn't feel like I had won before," Kerr said. "I kind of just squeaked in. I won by a shot. That's all that it takes. I've lost plenty of tournaments by a shot, but winning by a shot feels a lot better."
Park had led Kerr by two strokes after third round and was in formidable form, with 11 birdies to only one bogie in rounds two and three.
Four bogeys and four birdies later, however, the South Korean finished the fourth round with an even-par 72.
Still, the final leaderboard was a tight picture, with Kerr’s compatriot and second-round leader Angela Stanford shooting a 68 to match Park’s end total of 15-under 273.
And Kerr felt the pressure in those final holes.
"Yeah, I was nervous. I haven't been in this position to win in a while. To even have one putt to win, or two putts to win, I wasn't nervous for messing up, but it was hard to control the amount of adrenaline that was in my system,” Kerr said.
"I just tried to take some breaths and calm myself down and I still can't believe how hard I hit that first putt. I gave the fans and myself a heart attack, but I stayed in there mentally until the end."
Meanwhile, Lewis hit a 4-under 68, which was enough for equal fourth place with Candie Kung, but more significantly sealed the Player of the Year award.
Park had been her main rival for the accolade but would have had to win both this tournament and next week’s season-ending Titleholders to unseat her.
"After I finally made my last putt there on 18, I think it finally hit me," Lewis said. "It's just crazy to think that there have been so many great American players and I am the one after Beth in '94. It's just crazy to even think of."
Lewis clinched her fourth 2012 title last week in Japan and is rounding off her most successful professional season to date, with 16 top-10 placings so far.