Offstage, Zeppo had great mechanical skills and was largely responsible for keeping the Marx family car running. Zeppo later worked machining parts for the war effort during World War II.
On April 12, 1927, Zeppo married Marion Benda. The couple would adopt one child, Timothy, in 1944. They would later divorce on May 12, 1954. On September 18, 1959, Zeppo married Barbara Blakely. Zeppo and Blakely would divorce in 1973. (Blakely would later marry singer Frank Sinatra).