The 19-year-old singer recently got the animal as a gift from record producer Mally Mall, reported TMZ Online.
Bieber arrived at the airport and was confronted about the monkey when he went through customs. When the 'Baby' hitmaker was unable to produce proper documents, German officials decided to detain the monkey.
The animal is now in quarantine and Bieber could face prosecution from German authorities and a 10,000 pounds fine.
"He and Mally go everywhere together. He will be heartbroken. Justin has been acting like a right diva. He is out of control and lives in an alternative reality to the rest of us," a source said.