Wanger was born Walter Feuchtwanger in San Francisco. He was the son of Stella (Stettheimer) and Sigmund Feuchtwanger, who were from German Jewish families that had emigrated to the United States in the nineteenth century. Wanger was from a non-observant Jewish family, and in later life attended Episcopalian services with his wife. In order to assimilate into American society, his mother altered the family name simply to Wanger in 1908. The Wangers were well-connected and upper middle class, something which later differentiated Wanger from the other Jewish film moguls who came from more ordinary backgrounds.