After completing his studies, Åström began his career as an attaché at the Ministry for Foreign Affairs in Stockholm.

He served in the Soviet Union during World War II and later held posts in Washington, D.C., and London, rising to key leadership roles at the Ministry for Foreign Affairs.

[4] In 1964, Åström succeeded Agda Rössel as Sweden's Permanent Representative to the United Nations.

Åström's autobiography, Ögonblick: från ett halvsekel i UD-tjänst ("Moments: From Half a Century in the Duty of the Ministry for Foreign Affairs"), was published in 1992.

In an interview he has explained that his role as a diplomat made it impossible to declare himself as homosexual in public, but that his superiors and others were informed to eliminate the possibility of him being blackmailed by foreign agents.