In 1919 Wigforss was elected as a Social Democratic member of the First Chamber of the Swedish Parliament, representing Gothenburg, and he became a member of various committees. He was appointed a member of the third cabinet of Hjalmar Branting in 1924, and after Branting's resignation in January 1925, became a member of Rickard Sandler's cabinet. He was made temporary Minister of Finance on 24 January 1925 when Fredrik Thorsson fell ill, and succeeded him on 8 May of the same year, following his death. The Sandler cabinet resigned on 7 June 1926.