The accused has been identified as Amit, who worked for a multi-national Pizza outlet, police said.
The incident took place today morning when the victim was molested by the accused after she had come out play in the staircase of her residential building. There was no one at her home during the incident, they said.
A senior Delhi police official said, "the incident came to light when the girl told her family members about the pizza delivery boy who had touched her inappropriately while she was playing on the staircase."