Delhi Law Minister Jitender Singh Tomar was arrested on Tuesday, said AAP leader Sanjay Singh.
Singh said he spoke to the minister and tweeted: "Delhi Police arrested him without any notice or prior information."
The minister has been taken to the Hauz Khas police station, the tweet said.
Singh did not immediately specify the reason for his arrest.
Police sources, however, said an FIR in the fake degree case was registered against Tomar Monday night. He has been charged under various IPC sections including 420 (cheating).
The AAP ministser had last month urged the high court to stay the proceedings that the Bar Council of Delhi (BCD) initiated against him.
A police team had gone to Bihar on the direction of court to investigate charges that he had used fake degrees.
The Tilak Manjhi Bhagalpur University in Bihar had earlier told the Delhi High Court that Tomar’s provisional certificate is “fabricated and does not exist in the institution's record”.