Nomura was the last woman standing on a brutally windy day that turned into even more of a marathon as she and Kerr both parred the first five playoff holes -- all played at Las Colinas Country Club's par-five 18th hole.
As they returned for one more time before darkness fell, Nomura gave herself an eagle chance and tapped in from inches for the birdie. She then watched as Kerr's birdie attempt from outside 10 feet slid by.
Nomura captured her third LPGA crown, to go with the Women's Australian Open and Swinging Skirts LPGA Classic titles she won last year.
She had to dig deep to do so on a day when the scoring average was more than five strokes over par.
Nomura started the day with a two-stroke lead and did well in the conditions to finish the front nine in even par after one bogey and one birdie.
But she bogeyed 10 and 11, and dropped two more shots at 14 and 16.
She made a 12-footer to salvage a double-bogey at 17, but that left her a stroke behind Kerr who had made the only birdie of the day at the par-three 17th.
After Kerr had completed her three-over 74 for a three-under par total of 281, Nomura birdied the 18th for a five-over 76 that forced the playoff.
The top two finished regulation two strokes in front of American Jessica Korda, whose two-over 73 gave her a one-under total of 283 -- the only other under par total for the week.
South Korea's Park Sung-Hyun was fourth after a 74 for 284.