The rape incident took place on Thursday night on the Bangabandhu Bridge-Dhaka highway in the district.
The arrestee, identified as Nazmul, gave a confessional statement on Saturday.
Officer-in-Charge of Bangabandhu Bridge East Police Station Mosharraf Hossain said, the driver, supervisor and the driver’s assistant allegedly raped the girl around 11:30 pm after all other passengers got down from the bus in different stoppages.
A police patrol team ran into the spot and rescued the girl and arrested Nazmul hearing the scream of the girl, he added.
The girl was later sent to Tangail General Hospital.
Police are conducting drives to arrest the bus supervisor Bishu and driver Alam, who ran away from the scene.
The girl is primarily being suspected to be disabled as she cannot say anything except her name and name of her home district.
Nazmul was sent to jail on Friday afternoon.
On Saturday, primary sign of rape was found in the medical test, said Dr Rehena Parvin, Gynecologist of Tangail General Hospital.