Australia's acting governor-general, Tasmanian Governor Guy Green, was sworn by High Court Justice Dyson Heydon on Thursday.
According to the Australian Associated Press, the four-minute ceremony took place at the Government House in Canberra.
Governor-general Peter Hollingworth has stepped aside from the nominal state head post until a rape allegation against him is resolved in the Victorian Supreme Court.
It is widely believed that Hollingworth can hardly retake the position with increasing pressure urging him to resign.
Besides the rape allegation, he has been criticized since December 2001 for his way in dealing with a paedophile priest when he was Anglican Archbishop of Brisbane.
Prime Minister John Howard was reluctant to propose the Queen to sack Hollingworth, insisting the former Archbishop had no mistaking in the position as governor-general and he should have the right to clear his name through the court.
Hollingworth was present at the swearing-in ceremony.