The accused, identified as Imran, teaches Urdu and the complainant, a 14-year-old girl, was one of his students, said police.
According to the police, the incident came to light yesterday when the girl refused to go for tuition and her parents noticed abrupt change in her behaviour.
She later broke down and narrated her ordeal to her mother.
Her parents then reported the matter to the police.
The girl was then taken for a medical examination which confirmed sexual assault.
A case under relevant sections of IPC and POCSO Acts was registered at Govindpuri police station and the accused was arrested immediately.
The girl was later counselled by an NGO in the presence of her mother, police added.