The 50-year-old former priest, who worked at a school near the city of Kassel, said he had sexually abused six altar boys between 1992 and 2003. Investigators also found pornographic images of children on his computer.
The judge said the man deliberately targeted weak boys and seized upon their enthusiasm, and told him, "You used your authority and your position as a person of trust".
He also said there was no doubt about the priest's paedophile tendencies. "This is apparent in the deeds," the judge said.
"This will haunt the victims for life," the prosecution lawyer told the court. She was grateful for the fact that the defendant confessed in court, sparing the victims the ordeal of testifying.
The man, a trained educator, had filmed many of his assaults. He repeatedly applied the same scheme, feigning a medical or scientific examination to approach the children.
"You scared the children," the judge said.
The priest was suspended from his duties in May, when initial suspicions arose. He has been held in custody since June, and the priory he worked for has been disbanded by his religious order.
The priest asked forgiveness "from all those whose trust I abused". His defence lawyer said the priest had managed to end his abusive behaviour in 2003.