Kerr, 40, holed a 35-foot birdie putt on the final hole for a closing 71 and a 15-under-par 269 total, winning by a shot from two of her compatriots, Danielle Kang and Jacqui Concolino, as well as China’s Shanshan Feng.
“To do what I do for a living is amazing,” said Kerr, who is the 27th player in LPGA history to record 20 career wins.
“This tournament is a beacon for women’s health and raising awareness for breast cancer is near and dear to my heart. I’m so proud to be the champion of this tournament.”
Matthew was 42 when she won the Lorena Ochoa Invitational in Mexico in 2011.
Meanwhile, 17-year-old Chinese player Lin Yuxin is heading to Carnoustie next July to play in the 147th Open Championship.
The left-hander also earned a spot in The Masters as a reward for winning the Asia-Pacific Amateur Championship at Royal Wellington.
Yuxin birdied the 17th hole then eagled the last to card a six-under-par 65 and finish 14-under, three ahead of compatriot Andy Zhang (67), who was rewarded with a place in The Open Qualifying Series.