The 23-year-old female victim was in critical condition in a hospital.
Public anger and shock followed the attack Sunday in New Delhi in which the woman, a student of physiotherapy, was gang-raped by several men after she boarded the privately run bus with a male friend.
As the bus driver drove around, the woman and her friend were badly beaten, the woman repeatedly raped, and then she and her companion were stripped and tossed out of the vehicle, police said.
The two victims, discovered by a highway patrol, were admitted to a hospital.
No other passengers were aboard the bus at the time of the attack and curtains were drawn on the vehicle's tinted windows, preventing outsiders from knowing what was happening, investigators said.
Four other people, including the driver of the bus, had already been arrested, the BBC reported.
"The fifth accused has been arrested in the rape case. His age is being verified before giving details. If [he is a] minor, we have to hold back his particulars as per law," Delhi Police Chief Neeraj Kumar said Friday.
Police charged the suspects with attempted murder, destruction of evidence, kidnapping or abducting, gang-rape, unnatural offenses, hurting in committing robbery and common intention, the Press Trust of India reported.