He was an employee of SAAB from 1944 to 1946, the Swedish National Defence Research Institute (FOA) from 1946 to 1950, and the semi-governmental nuclear energy company AB Atomenergi from 1950 to 1954.

[2] In 1964 he accepted a position at Lund University and was appointed professor of elementary particle physics there the following year.

[4] Guy von Dardel was elected a member of the Royal Swedish Academy of Sciences in 1975.

Guy von Dardel was active in searching for and establishing the fate of his half-brother, Raoul Wallenberg, who was apprehended by Soviet troops in Hungary towards the end of the Second World War and subsequently disappeared.

[5][6] Dardel was a member of several international commissions which inquired into the matter, including the Swedish government's Wallenberg committee (Wallenbergutredningen) which presented its report in 2001, after ten years of work.