Father Brennan, 74, was arrested and charged last Thursday with two counts of misprision of a felony - failing to disclose a serious crime - relating to alleged child sex offences by defrocked priest John Denham against two boys in the late 1970s.
The offences allegedly occurred at St Pius X, in the Newcastle suburb of Adamstown, where Father Denham was a teacher and Father Brennan was school principal.
Strike Force Georgiana's Detective Sergeant Kristi Faber also charged Father Brennan with eight counts of sexually assaulting a boy, 8, at a Waratah church in 1984 and 1985, and two counts of assault.
Dr Bernard Barrett, of the victims rights support group Broken Rites Australia, described the charges as ''a milestone in Australia''.
''These charges are of Australia-wide significance,'' Dr Barrett said. ''It's the first time such a senior Catholic church leader has been charged with allegedly concealing child sex crimes by another alleged offender.''
The charges were laid only months after international publicity over the first American conviction of a senior Catholic priest for hiding the child sex crimes of another priest.
One of the men from the Hunter Valley, who alleged Father Brennan caned him in 1978 after he alleged Father Denham had repeatedly sexually assaulted him at the school, thanked police for a determined investigation.
''If this makes one person stand up and say, 'This is what happened to me', then I'll feel better,'' he said.
Another Hunter man, who also alleged Father Brennan caned him after he alleged Father Denham had repeatedly sexually assaulted him at the school, said it was ''great news''.
''I feel better now that I've got it off my chest after saying nothing for all these years, but there's still a dark side of it,'' he said.
The Maitland-Newcastle bishop, Bill Wright, announced the charges in a statement issued ''with profound sadness''.
While the charges represented ''most grievous crimes'', Father Brennan was entitled to the presumption of innocence ''during a legal process of unknown duration'', the bishop said.
''We must also find the strength within us to support those who will look to the church to again explain the inexplicable.''
The charge of misprision of a felony was replaced in the NSW Crimes Act in 1990 by a package of concealing serious crimes offences under section 316.
Father Brennan was charged with the older offences because the allegations relate to the late 1970s.
He will appear in court on September 25.
Father Denham has not entered pleas to 47 charges including indecent assault and buggery involving 14 boys in the 1970s.
He will return to court next month.