According to the airline, flight 9W 202 -- operating between Delhi and Doha -- was on Monday diverted to Karachi following a medical health emergency on board.
However, the passenger requiring urgent medical attention succumbed when the plane landed in Karachi.
The aircraft returned to Delhi on Tuesday morning, the airline said.
"One of the guests developed a medical condition and the captain decided to land at the nearest airport given the emergency," the airline said in a statement.
"Medical assistance was duly coordinated prior to the flight's arrival, however, the guest succumbed on arrival in Karachi."
The airline added that there were 141 passengers on board the Boeing 737 aircraft.