Mogens Bruun Jensen is born on 18 March 1925 in Odense, Denmark.
He enlists for the Royal Australian Air Force on 16 October 1943 in Perth. He is then living in East Fremantle. He is discharged on 28 June 1945 at which point he is attached to Brisbane Medical Unit holding the rank of Leading Aircraftman.
Mogens Bruun Jensen applies for naturalization in 1950.