Arness was born in Minneapolis, Minnesota. He dropped the "u" when he started acting. His mother was of German ancestry; his father was of Norwegian ancestry. The family name had been Aursnes, but when Rolf's father, Peter Aursnes, emigrated from Norway in 1887, he changed it to Aurness. Arness and his family were Methodists. He served in the army in Italy during World War II. He received the Bronze Star.