FIFA have cleared Croatia Under-21 international Fran Karacic to switch eligibility and play for the Socceroos at the 2018 FIFA World Cup.
FIFA say the formal 'change of association' for Croatia-born Karacic, who is named in Australia's provisional squad, was completed on Thursday.
The 22-year-old defender is eligible for Australia because his father was born there.
FIFA let players make one change of allegiance in their career before they play a senior competitive game for a national team.
Karacic seems certain to be included in coach Bert van Marwijk's 23-man squad next month in Russia to fill a need at right-back.
He helped Lokomotiva Zagreb finish fifth in the Croatian league this season.
Australia will play in Group C with France, Denmark and Peru.