The Trier bishopric in the west of the country said on Monday the "shocking" allegations involved crimes committed from the 1950s to 1990.
"For my part, I would like to encourage those victims who have not yet found the courage to come forward to do so," Bishop Stephan Ackermann told reporters, saying he was "stunned" by the cases that had come to light.
Ackermann said two people had already reported their cases to authorities while the Church had passed on information on an additional three to prosecutors.
Ten of the accused priests have since died, another two have retired.
Ackermann said the diocese was still conferring on how to handle three cases that fell under the criminal statute of limitations.
He said that beyond the new cases that had surfaced, three priests had been convicted of abuse in the 1990s.
Meanwhile, the prosecutor's office in the central city of Fulda confirmed sexual abuse charges had been filed against a former priest who had worked in nearby Erfurt.
It said the man had been previously charged with pedophilia but declined to provide further details.
Germany's Catholic Church has been thrown into crisis in recent weeks as dozens of people have come forward alleging they were abused as minors by priests. Most cases date back several years.
Similar scandals have also erupted in the Netherlands, Austria and Switzerland, while Ireland has been rocked by revelations about cover up efforts by the head of the Church there in the 1970s.
The Vatican has said it received 3000 reports between 2001 and 2010 of sexual abuse of children by Catholic clergy committed over the past 50 years.
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