The aircraft -- A340-300 -- took off from the Indira Gandhi International Airport here at around 1627 hours but was forced to return soon.
"At 1650 hours, ATC declared full emergency for Mahan Air flight W5-070, aircraft type A340-300, due to one engine failure," the official said.
The flight departed from the national capital for Tehran at 1627 hours and returned on full emergency. Flight landed safely on runway 28 at 1713 hours, the official added.
Mahan Air is a private carrier based in Tehran, Iran.