The arrestees were identified as auto-rickshaw driver Md Mamun, 18, son of Anwar Hossain of Bairag union in Anowara upazila, and Md Helal Uddin, son of Abdul Gafur of Dakkhin Chanhura village in Patiya upazila.
Dulal Mahmud, officer-in-charge of Anowar Police Station, said the arrestees confessed to their involvement in the gang-rape.
They also disclosed the names of two other culprits, he said.
The 15-year-old girl was raped by the auto-rickshaw driver and its passengers while she was returning home in Chandanaish upazila from her factory in Korean Export Processing Zone in Anowara on Wednesday.
Locals spotted the victim in an unconscious condition at Chatri around 8pm and took her to Chittagong Medical College Hospital (CMCH) where she regained her senses the following day.