Luns attended a gymnasium in Amsterdam from April 1924 until June 1930. Luns was conscripted in the Coastguard of the Royal Netherlands Navy serving as a warrant officer from June 1930 until July 1931. Luns applied at the University of Amsterdam in July 1931 majoring in law before transferring to the Leiden University in November 1932, obtaining a Bachelor of Laws degree in June 1933 and graduating with a Master of Laws degree in July 1937. Luns applied at the London School of Economics of the University of London in January 1938 for a postgraduate education in economics, obtaining a Bachelor of Economics degree in June 1938. Luns worked as a civil servant for the Diplomatic service of the Ministry of Foreign Affairs from October 1938 until September 1952 as an attaché in Bern, Switzerland, from December 1939 until April 1942, as an attaché in Lisbon, Portugal, from April 1942 until November 1943, as an attaché in London, England, from November 1943 until September 1949 and as chargé d'affaires at the United Nations in New York City from September 1949 until September 1952.