Joaquin Niemann started the day four shots behind the lead and shot a 66 at The Australian Golf Club setting the clubhouse target at 14-unde at the ISPS HANDA Australian Open.
Overnight co-leader Rikuya Hoshino of Japan carded a 70 to join him in a sudden death playoff. Both players birdied the first hole before Niemann holed a seven-foot eagle putt at the 18th to win his first DP World Tour title.
"It was a nice day. These last two playoff holes showed how I have been playing the last few weeks here in Australia," said the Chilean.
"My putting hasn't been the best, but I've been working hard on it and it was nice to make that last putt.
"I always practise those three, four, five-feet ones and know that one of those will be to win a tournament. It's amazing."
Australia's Min Woo Lee started the day with a share of the lead but made a single birdie and two bogeys on Sunday to close with a 72 and solo third place at 12-under.
Scotland's Grant Forrest and Australia's Adam Scott both closed with 68s to tie for fourth place at 11-under alongside England's Laurie Canter whose own 68 was bogey-free.
Scott joins Niemann and Hoshino in qualifying for next year's 152nd Open at Royal Troon as Lee was already qualified.