Police said the girl and the 14-year-old boy were watching television at her house on May 20 when the incident occurred.
The girl's mother caught the teenager raping the child and filed a complaint today, following which he was arrested.
Police said a case was registered against the boy under Section 7 and 8 of the Protection of Children from Sexual Offences Act. He was produced before a judicial magistrate and sent to Salem Central prison.