Gelling was previously with Sydney Roosters but he was sacked in 2010 after being accused of defecating over a hotel room.
Warriors head coach Shaun Wane said the youngster had been highly recommended by Wigan legends Kevin Iro and Dean Bell.
He said: “He maybe unknown to the rugby league public in the UK, however, some of English Rugby League’s most successful imports have come over with similar reputations.
“Players like Kevin Iro, Henry Paul, Frano Botica and even George Carmont were little known over here but proved to be world class acquisitions.
“I know he has learned from his experience both at the Roosters and in New Zealand and comes to the club fully prepared to buy into the Wigan culture and establish himself as a firs team player.”
Gelling has been handed squad number 24 and is due to fly out to Florida with his new team mates for the Warriors pre-season training camp today.
He said: “I am delighted to be here and am really looking forward to getting straight into training with my new team mates.
“It will be an honour to play for the world-famous Wigan club and I’ve already heard about how passionate the Warriors supporters are.
“I know the squad is packed full of talent so I will have to work hard to earn the opportunity to show the coaching staff and fans exactly what I can offer.”