The study was commissioned by the Church itself, and was due to be published on 25 September.
According to the report, some 1,670 clergymen in Germany committed some form of sex attack on 3,677 minors, German outlet Spiegel Online reported.
A Church spokesman said it was "dismayed and ashamed" by the findings. The report is the latest in a long series of revelations that have uncovered decades
According to the new study, only 38% of the alleged perpetrators were prosecuted with most facing only minor disciplinary procedures, German media said. About one in six cases involved rape.
Most of the victims were boys, and more than half were aged 13 or younger. Predatory clerics were often moved to new communities, where no warning was issued about their actions.
The study was compiled by three German universities, using 38,000 documents from 27 German dioceses. Its authors said the true extent of the abuse may be even greater, as some records were "destroyed or manipulated".
How has the Catholic Church reacted?
"We know the extent of the sexual abuse that has been demonstrated by the study. We are dismayed and ashamed by it," said Bishop Stephan Ackermann, a spokesman for the German Bishops' Conference which commissioned the report.
He said the aim of the study was to shed light on "this dark side of our Church, for the sake of those affected, but also for us ourselves to see the errors and to do everything to prevent them from being repeated".
"I stress that the study is a measure that we owe not only to the Church but first and foremost, to those affected," the bishop added.
