Matsuyama clinched his fifth win in his last nine starts worldwide when he sank a 10-foot birdie putt on the fourth playoff hole, the driveable par-four 17th, where Simpson could only par.
The duo had finished the 72 regulation holes on 17-under 267, Matsuyama narrowly missing a birdie putt at the last to card a five-under 66 and Simpson closing with a best-of-the-day 64.
It was Matsuyama's fourth career win on the PGA Tour and Shigeki Maruyama (with three) is the only other Japanese player with multiple victories on the US circuit.
"It was a struggle, especially that playoff, but I am really happy to win," Matsuyama, 24, told CBS Sports via an interpreter after claiming the Phoenix Open title for a second year in a row at the fourth extra hole.
