Tahir alias Vinit was arrested Wednesday from the Dwarka area in west Delhi, police said.
The incident took place Aug 20 when the 16-year-old domestic help, after finishing her work in an apartment in Dwarka Sector 4, was waiting for a bus.
Her friend, Suraj in his early 20s came by in his car and offered her a lift. On the way she had a cold drink which was allegedly laced with sedatives and given to her by Suraj.
As she fell unconscious, she was taken to a nearby garage and raped by Suraj and his two unidentified accomplices. The men also destroyed her mobile phone.
The girl somehow managed to escape and reached a PCO booth nearby owned by her friend Tahir, who after hearing of her ordeal took her to his house, held her captive and raped her repeatedly.
The girl's family lodged a complaint with the police Aug 24. The girl was found lying unconscious near a bus stand in Dabri in west Delhi Aug 25.
A medical test on the girl confirmed rape, said the police, adding that after a month-long investigation, Tahir was finally arrested Wednesday.
The hunt for the other three accused is now on.