There were no immediate reports of any casualties, officials said.
Thick smoke could be seen billowing out of the building in Sector 12. People were standing on ledges in balconies as rescuers tried to reach them by breaking window panes.
Staffers tried to help patients out of the building in Noida, on the outskirts of the national capital.
Fire tenders rushed to the spot to carry out rescue operations and douse the flames.
"A fire has broken out in the Metro hospital. Rescue operations are underway," an official said.
The cause of the fire was not immediately known.
