Petaia missed most of the Super Rugby season due to a Lisfranc injury but the exciting 19-year-old back is set to feature at the World Cup, which gets underway on 20 September.
The Reds sensation was set to make his debut against Italy last year, however, a hamstring injury delayed his international bow for 2015 World Cup runners-up the Wallabies.
Now, Petaia – the only uncapped player in Michael Cheika's squad – is poised to become the youngest World Cup player in Australia history.
There are not too many surprises in the Wallabies team, though Cheika opted to select just two half-backs in Will Genia and Nic White, with Joe Powell left out and giant lock Will Skelton not on the list.
"We've become a really tight group and it was a very difficult process in picking only 31 players, but I know each player selected will travel to Japan with the full support of those team-mates who won't board the flight," said Cheika, who included Powell, Tom Banks, Liam Wright, Luke Jones and Tatafu Polota-Nau as extended members for the team's pre-World Cup camp and Test against Samoa.
"We have worked really hard at building each week and each game so far this season and play a brand of Rugby that Australia would be proud of and get every player contributing towards the outcome.
"It's also important that we select a squad that will handle the tournament play and our draw in particular at the Rugby World Cup, as well as maintain a strong competition for places in the team.
"These next few weeks are about building and adding that little extra edge as a squad and we'll be working hard to make sure we deliver on the qualities we want people to see when we run out on the field in Japan.
"We have five extra train-on members coming with us to New Caledonia and then we'll return to take on Samoa, who we have had great clashes with in the past."
Australia will face Samoa in Sydney on September 7 before kicking off their World Cup campaign against Fiji on September 21.
The Wallabies are also scheduled to meet Wales (September 29), Uruguay (October 5) and Georgia (October 11) in Pool D.
Australia's 31-man Rugby World Cup squad in full:
Forwards: Allan Alaalatoa, Rory Arnold, Adam Coleman, Jack Dempsey, Folau Fainga'a, Michael Hooper, Sekope Kepu, Tolu Latu, Isi Naisarani, David Pocock, Izack Rodda, Lukhan Salakaia-Loto, Rob Simmons, Scott Sio, James Slipper, Taniela Tupou, Jordan Uelese.
Backs: Adam Ashley-Cooper, Kurtley Beale, Bernard Foley, Will Genia, Dane Haylett-Petty, Reece Hodge, Samu Kerevi, Marika Koroibete, Tevita Kuridrani, Christian Lealiifano, James O'Connor, Jordan Petaia, Matt To'omua, Nic White.