Green's final round of 67 was good enough to see him come from three shots behind third round leader, Jason Scrivener, to snatch the title with a birdie at the 18th hole the second time around in extra time.
Cullen birdied the par 5 72nd hole to force the playoff and despite losing, the South Australian continues a very impressive summer.
The playoff pair finished two shots clear of former Australian amateur champion Scott Arnold and local amateurs Ryan Ruffels and Ben Eccles.
The victory capped a superb week for Green who just last week played the Dubai Desert Classic. His albatross hole in one during the week created a lot of profile for him and the event and in addition his new fiancÃƒÂ©e Marianne Skarpnord secured the Victorian Women's Open which was played concurrently with the men's at the same venue.
Norwegian Skarpnord won by three over local Su Oh and England's Holly Clyburn while Rachel Hetherington showed her comeback is on track with a round of 68, the best of the day, to finish tied for 4th with NSW's Rebecca Artis.
The PGA Tour of Australasia now plays the Victorian PGA Championship at the Huntingdale Golf Club while the ALPGA now heads to the Gold Coast for the RACV Ladies Masters.
Want video tips delivered straight to your inbox? Subscribe to iseekgolf.com newsletters.