Gyllenstierna served as Swedish envoy to the Soviet Union, Iran, Iraq, Turkey and Greece from 1937 to 1939.

He passed mogenhetsexamen in 1900 and received a Juris utriusque candidate degree from Lund University on 15 December 1909.

[1] He became acting extra head of department at the Ministry for Foreign Affairs on 29 October 1918 and first legation secretary in Helsinki on 12 September 1919.

He was then legation counsellor and head of the Trade Policy Department's 3rd Bureau at the Ministry for Foreign Affairs from 28 August 1922 but became legation counsellor and head of the Political and Trade Policy Department's 3rd Bureau at the Ministry for Foreign Affairs from 1 September.

[2] Gyllenstierna was legation counsellor in London from 11 February 1927 and was appointed on 6 August 1930 to become envoy in Moscow from 1 October the same year.