The attacking midfielder was born and raised in Sydney but has Italian heritage.
Although he played for Italy at youth level, he never received a senior cap and so still qualified for Australia.
The 22-year-old switched allegiance to Australia in late May which ruffled some feathers given he had turned down the chance to play for the Socceroos at the last World Cup under Graham Arnold.
"When I was 18, maybe I was a bit too young, and maybe I was a bit too scared to make the change straight away," he said of snubbing Australia in 2022.
"Maybe I was in my comfort zone a bit, playing for Italy.
"Something, I don't know, in my heart just said 'I think it's time to come home'."
It was a boost for Australia after injured Middlesbrough midfielder Riley McGree was ruled out of the World Cup.
Volpato made his first appearance for Australia in the pre-World Cup friendly 1-1 draw against Switzerland in San Diego on Saturday.
He is still acclimatising after his late arrival in training camp and was substituted at half-time.
Volpato plays for Serie A side Sassuolo and said he spent a long time talking with fellow Australian and Parma defender Alessandro Circati about his decision.
"I'm Italian and I'm Australian, so it's actually been a big decision that's always been on my head 24/7 for quite a while," Volpato said.
"Obviously, I do feel Australian, so it felt really good coming in, being brought in by the boys, and speaking English -- Aussie."
