He is the second person in Delhi to test positive for the infection. He has no recent history of foreign or local travel, sources told PTI.
The Nigerian national is admitted to the Delhi government-run LNJP Hospital, the nodal hospital for treatment of the infection.
He has blisters and fever for the last five days.
His samples were sent to the National Institute of Virology (NIV) in Pune. The report which arrived Monday evening showed he was positive, an official source said.
Two suspected patients of monkeypox, who are of African origin, have also been admitted to the LNJP Hospital, sources added.
(With inputs from PTI)