Pell, at a news conference in Rome on Thursday, said he had been the victim of "relentless character assassination."
"I'm innocent of these charges, they are false," Pell said. "The whole idea of sexual abuse is abhorrent to me."
The alleged victims have not been named, and police have not released any information on the case except to say there are "multiple complainants."
Pell is a top advisor to Pope Francis and the third-ranking official at the Vatican.
He's taking a leave of absence to fight the charges, and is expected to return to Australia to battle the allegations, the Archdiocese of Sydney said in the statement on its website.
More than four dozen Catholic bishops worldwide and dozens of priests have been accused of sexually assaulting children in alleged incidents dating back more than 50 years.