The 53-year-old will undergo years of therapy in a closed psychiatric institution before starting his prison term, a court in the southeastern city of Deggendorf ruled.
Whether he will ever be released depends on whether he is still deemed a threat to society, said chief justice Thomas Trautwein.
Previously named in media reports as Thomas Maria B., the former priest had previously been jailed from 2003 to 2009 for other sexual crimes.
He later obtained new church qualification papers to work as a priest using forged documents.
In his latest trial, he was found guilty of sexually abusing five boys in 108 cases since the 1990s.
He was also convicted of the attempted rape of an 18-year-old girl, as well as assault and possession of child pornography.
The abuses were committed around the German cities of Mainz and Deggendorf as well as in Austria, Switzerland, Italy and Poland, the court was told.