The Italy-based playmaker, who turned down a chance to play for Australia at the 2022 World Cup, is one of two uncapped players in the squad, along with Japan-based striker Tete Yengi who was a surprise call-up to the team's pre-tournament camp in Florida.
Volpato only joined the squad early on Saturday, a day after his decision to ditch Italy was confirmed by Football Australia.
Yengi, the younger brother of fellow Australia forward Kusini Yengi, was selected after missing the 1-0 friendly loss to World Cup co-hosts Mexico at the Rose Bowl on Saturday.
Popovic had telegraphed the core of his squad from his selections at the Sarasota camp but had a few hard choices to make after the Mexico defeat.
He ultimately decided on Patrick Beach as his third goalkeeper at the expense of Joe Gauci, with captain Mat Ryan to start in the Socceroos goal and Paul Izzo to deputise.
Yengi's inclusion meant no place for forward Brandon Borrello, while winger Martin Boyle was also cut four years after an injury ruined his hopes of playing at Qatar 2022.
Defender Kye Rowles also missed out on the 26-man squad.
"Some difficult decisions had to be made – that’s the nature of major tournaments," Popovic said in a statement.
"But it’s also a credit to all the players involved over the past few weeks who worked extremely hard during an extended and challenging pre-camp."
The squad includes 17 World Cup debutants, including 18-year-old defender Lucas Herrington and 21-year-old Sydney FC midfielder Paul Okon-Engstler who was rewarded for good form in the A-League.
Central defender Harry Souttar and winger Mathew Leckie, Australia's heroes at Qatar 2022, have been included after coming back from long battles with injury.
Melbourne Victory's Nishan Velupillay and Awer Mabil join Nestory Irankunda and striker Mohamed Toure in Popovic's forward setup.
Australia World Cup squad:
Patrick Beach, Aziz Behich, Jordan Bos, Cameron Burgess, Alessandro Circati, Milos Degenek, Cameron Devlin, Jason Geria, Lucas Herrington, Ajdin Hrustic, Nestory Irankunda, Jackson Irvine, Jacob Italiano, Paul Izzo, Mathew Leckie, Awer Mabil, Connor Metcalfe, Aiden O’Neill, Paul Okon-Engstler, Mat Ryan, Harry Souttar, Mohamed Toure, Kai Trewin, Nishan Velupillay, Cristian Volpato, Tete Yengi
