He started working as a mailman in 1940 while attending evening gymnasium courses, and received his students' degree in 1944.

Andersson then began studying economics and political science at Stockholm University College, but did not graduate.

[1] In 1942 Andersson joined the Swedish Social Democratic Youth League, of which he chaired the local chapter from 1945 to 1948.

[2] As Foreign Minister, Andersson worked strongly for peace in the Israeli–Palestinian conflict, and took initiatives for dialogue between Israel and the Palestine Liberation Organization.

After his ministerial career ended, he served as President of the Nordic Council in 1994 and as Chairman of the Olof Palme International Center until 1999.