The present site of RAF St. Mawgan was opened as a civilian airfield in 1933. It was requisitioned at the outbreak of World War II and named RAF Trebelzue. It initially served as a satellite of nearby RAF St. Eval but was expanded with twin concrete runways. In February 1943 it was re-named RAF St. Mawgan. In June 1943, the United States Army Air Force took over and carried out a number of major improvements, including a new control tower and a further extension of the main runway. The base was put under maintenance on 1 July1947.
In 1951 it reopened as a Coastal Command base used for maritime reconnaissance, flying Avro Lancaster and Avro Shackleton aircraft. In 1969 the first Nimrod aircraft arrived, and continued present until 1992 when maritime reconnaissance operations there ceased. In 2004 it is primarily used as a Search and Rescue base and is home to a flight of Sea King helicopters, as well as the maintenance centre for Sea Kings. No 1 Squadron RAF Regiment is based there, as is the School of Combat Survival and Rescue. St. Mawgan remains a Military Emergency Diversion Airfield with its 2745m main runway, and commerical flights operate from there.
St Mawgan is the home of the Joint Maritime Facility, commissioned 18 August1995, a command for undersea tracking operated by the Royal Navy and United States Navy.
According to the round of defence cuts announced in 2004, RAF operational flying will cease in 2006, with the Search and Rescue operations moving to RAF Valley.