The 22-year-old attacking midfielder, a dual citizen who was born and raised in Sydney, plays for Sassuolo in Serie A.
He turned down a chance to play for Australia at the 2022 World Cup, and another approach from Australia coach Tony Popovic earlier this year looked to have foundered when Volpato said he was happy to "wait for Italy".
Football Australia said they had received a release letter from their Italian counterparts and lodged paperwork with FIFA for "change of association clearance to ratify Volpato's decision to switch allegiance to Australia".
"Once cleared, Volpato will be eligible to officially represent the Socceroos," the governing body said in a statement.
The news comes days after Australia lost playmaker Riley McGree for the tournament because of a hamstring injury he sustained playing for English club Middlesbrough.
Popovic will name his final 26-man squad for the June 11 to July 19 tournament in the United States, Canada and Mexico on Monday.
Australia play Turkey, the U.S. and Paraguay in the opening-round group stage, kicking off their campaign against the Turks in Vancouver on June 13.