During the Second World War, he was responsible of the Swiss programme to reduce food imports and increase agricultural production, which consisted mainly in extending the cultivation area, and reducing meat production in favour of cereals production. The programme was called after his name, as Wahlen Plan.
He was elected to the Swiss Federal Council on 11 December 1958 and handed over office on 31 December 1965. He was affiliated to the Party of Farmers, Traders and Independents (BGB/PAI), now the Swiss People's Party.
During his time in office he held the following departments:
- Department of Justice and Police (1959)
- Department of Economic Affairs (1960)
- Political Department (1961)
- Department of Economic Affairs (1961)
- Political Department (1962–1965)
He was President of the Confederation in 1961.
- Empire of Iran : Commemorative Medal of the 2500th Anniversary of the founding of the Persian Empire (14/10/1971).