Sassuolo playmaker Volpato headlines Australia's 26-man squad along with 25-year-old uncapped striker Tete Yengi, while skipper Mat Ryan and veteran Mathew Leckie head to a fourth World Cup.
But it was heartbreak for veteran Martin Boyle, defender Kye Rowles, forward Brandon Borrello and goalkeeper Joe Gauci, who were all cut by coach Tony Popovic.
"A range of factors has gone into selecting this final World Cup squad," Popovic said in a statement.
"Some difficult decisions had to be made - that's the nature of major tournaments."
The squad features 17 players selected for their first World Cup, including 18-year-old defender Lucas Herrington.
The Socceroos play a friendly against Switzerland in San Diego on Saturday, then group games against Turkey, the United States and Paraguay.
Sassuolo winger Volpato, 22, only arrived in camp on Saturday morning (local time) - too late to feature in that night's 1-0 loss to Mexico - after switching his allegiance.
Volpato knocked back Graham Arnold's pitch to join Australia's 2022 World Cup squad, then in March said he was waiting for a call-up from Italy's senior team, before his change of heart.
Yengi, younger brother of fellow Socceroo Kusini Yengi, was selected despite not playing against Mexico.
Harry Souttar and Leckie make the squad after their first Socceroos appearances since 2024 against Mexico.
Rowles, a starter in 2022, misses out as does Boyle - who was injured ahead of Qatar and again falls agonisingly short of reaching a World Cup.
SOCCEROOS WORLD CUP SQUAD
Patrick Beach (GK)*, 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 (GK)*, Mathew Leckie, Awer Mabil, Connor Metcalfe*, Paul Okon-Engstler*, Aiden O'Neill*, Mat Ryan (GK), Harry Souttar, Mohamed Toure*, Kai Trewin*, Nishan Velupillay*, Cristian Volpato*, Tete Yengi*
* First World Cup selection
6°C