803 Squadron was re-formed (with Fairey Fulmar I) in October 1940, and after that served in the Eastern Mediterranean off HMS Formidable, fighting at the Battle of Cape Matapan (shooting down two aircraft and damaging two more) and providing fighter cover for the Malta convoys and the evacuation of Crete.

Next it was based in Palestine for operations against Syria from June 1941, then in August 1941 was merged into the RN Fighter Squadron (a combined unit fighting in the Western Desert).

Re-equipped again with Fairey Fulmar II in March 1942, it next operated from Ceylon against the Japanese (such as against the Easter Sunday Raid), rejoining HMS Formidable in the Indian Ocean in April.

The new combined squadron was disbanded at Tanga in August 1943, and only re-formed in June 1945 ready to join 19th Carrier Air Group in the Far Eastern theatre.

It then moved to HMS Ark Royal, where the greater hangar capacity meant that the squadron's standard strength could be doubled to 16 aircraft.

In August 1968, the squadron demonstrated the FAA's ability to reinforce forward-deployed carriers, when a flight of four Buccaneers flew from Britain to in the Indian Ocean, joining Hermes.