He was born in Kristiansund as a son of school manager Kristen Fostervoll (1856–1920) and Anna Karoline Kvande (1863–1941).

Fostervoll was later a board member of Noregs Mållag from 1931 to 1932 before returning to politics as local chapter leader of the Labour Party in Gloppen from 1934 to 1938.

[1] After the Second World War, Fostervoll was drafted into Gerhardsen's First Cabinet as Minister of Education and Church Affairs.

He had been elected to the Parliament of Norway for the Market towns of Møre og Romsdal county in the 1945 election, and while Gottfred Hoem had taken his seat while he was a cabinet minister, Fostervoll now assumed his seat in Parliament and chaired the Standing Committee on Education and Church Affairs for the rest of the term.

[2] During his time as a Minister, some important reforms went through, including the foundation of the Norwegian State Educational Loan Fund and the University of Bergen.

He served in this job from 1948 to 1962, the major achievement being the introduction of television in Norway (experimental broadcasts from 1954 and full service from 1960).