Victims stood and clapped as one of the most notorious paedophile priests in NSW was sentenced to 29 years' jail after committing 62 acts of child sex abuse in regional NSW.

Former Catholic priest John Joseph Farrell, 62, sexually abused nine young altar boys and three girls between 1979 and 1988 in Moree, Armidale and Tamworth.

Farrell, also known as "Father F", committed 27 acts of sexual assault, 48 acts of indecent assault and four acts of indecency.

The "predatory" former priest was sentenced to a maximum of 29 years but a minimum of 18 years at Sydney's Downing Centre District Court on Monday.

He closed his eyes and showed no emotion during the three hour sentencing.

One of the people who clapped and cried was victim Mark Boughton and his wife, Belinda.

Outside court he said he hoped the outcome would allow himself and other victims to "have a life".

"I'm very happy with the outcome; maybe it might show everyone else that they can stand up do the right thing and get these so called people off the street," Mr Boughton said.

"Hopefully, everyone can get on, move on, have a life," he said.

"Justice is served - he got what he wanted or what he needed, preying on kids. It's not on - hopefully the world knows that now."

During the sentencing hearing, Judge Peter Zahra spoke of how Farrell groomed many of his victims and exploited his position as a priest.

"The offender admitted he had a great deal of influence over the altar boys and he abused that position," Judge Zahra said.

Judge Zahra said the offender, "disregarded and took advantage of the vulnerability of the child victims".

"In relation to the altar boy victims, the offender knew there would be continuing opportunity because of the relationships he had developed with the victims and their parents.

"The offender created situations where he was confident he would not be detected even where his sexual abuse was, at times brazen in the extreme."

During the trial, Crown prosecutor Bryan Rowe outlined a series of incidents in which Farrell groped, molested, raped or forced oral sex on the altar boys.

One altar boy who was indecently assaulted in a Moree swimming pool and later raped in the presbytery said, "It was the worst memory of [my] life."

The victim went to report the sexual abuse to police in 2012 after viewing a Four Corners program.

He said he felt "embarrassed" and "ashamed" and said he hadn't come forward earlier because "back in 1982 no one would have believed my words against a priest".

Another victim had told the court that he was forced to perform oral sex on Farrell in a cellar when he was aged 10 or 11.

He said he told one of the brothers that he had been "hurt".

Someone told him "they would sort it out" so the victim felt safe when he went back to church the following day.

But Farrell pulled his pants down at the altar and raped him.

"It felt like hours," the victim said.

He said Farrell had threatened to kill him and his family if he told anyone about what had happened.

The former priest also molested three young girls. On one occasion he fondled the vagina of a little girl while she was at the dinner table with her family.

"The offender continued this conduct throughout the course of the meal during which he was engaging in conversation with other members of the family at the table," Judge Zahra said.

Another victim, who was aged between nine and 11, was in Farrell's bedroom at the presbytery when he was sexually assaulted with a toothbrush.

"I just want you to tell me if this hurts" or "how does this feel", Farrell said at the time.

The victim cried and screamed out in pain.

Farrell was not suspended from public ministry until 1992.

His jail term will expire in 2044 but he will be eligible for parole in June 2033.