Aandahl graduated from Litchville High School; from the University of North Dakota, Grand Forks in 1921 and became a farmer. He was superintendent of Litchville's schools from 1922-1927. In 1931, 1939 and 1941 he was member of the North Dakota state senate. From 1945-1950 he was governor of North Dakota.
He was elected as a Republican to the Eighty-second United States Congress (January 3, 1951-January 3, 1953). He was not a candidate for the Eighty-third Congress in 1952, but was an unsuccessful candidate for the United States Senate. From 1953 to 1961 he was appointed Assistant Secretary of the Department of the Interior.
Aandahl died on April 7, 1966, in Fargo, North Dakota and was intered in Hillside Cemetery, Valley City, North Dakota.