Andersen met Eleanor Anne Johnson (1911–2011) at Grace University Lutheran Church while they were both students. She was the eldest child of Gustav A. and Elizabeth Johnson, both Swedish immigrants. The Andersens were married on September 1, 1932. Her sister Edith Johnson later married future Minnesota Senator Stanley W. Holmquist. The Andersens settled in the Twin Cities. Eleanor decided to leave the university when they were married and postpone the completion of her degree. The two had a very happy marriage, and Andersen credited his wife for many of his accomplishments. They were the parents of three children. Several years later, she earned her bachelor's degree.