"There are doubts. 'In dubio pro reo'," he said using a Latin expression meaning that a defendant may not be convicted by the court when doubts about his or her guilt remain.
"We must avoid a media verdict, a verdict based on gossip," he told journalists aboard the papal plane during the return trip from Poland, where he had headlined a Catholic youth festival.
Explosive allegations emerged against the Australian cardinal last week with two men now in their 40s saying Pell had groped them during the 1970s.
The Australian Broadcasting Corporation which aired their claims also alleged Pell was naked in front of three young boys, believed to be aged eight to 10, in a Torquay surf club changing room in summer 1986-87.
Pell, 75, has denied the allegations and suggested there was a conspiracy against him.
The allegations come just months after Pell admitted he "mucked up" in dealing with paedophile priests in Victoria in the 1970s, while giving evidence to a national inquiry into institutional responses to child sex abuse.
He was accused of historic sex abuse claims when he was the Catholic Archbishop of Sydney in 2002, but was later cleared of any wrongdoing.
Pell was ordained in Rome in 1966 before returning to Australia in 1971 and rising to become the nation's top Catholic official.
He left for the Vatican in 2014 after being hand-picked by Pope Francis to make the Church's finances more transparent, although his powers were reined in earlier this month.
