In November 1939, Paramount signed Ryan to a six month contract and announced he would play the lead in Golden Gloves (1940), citing his boxing experience at Dartmouth. However, after a screen test with Gloves director Edward Dmytryk, the lead went to Richard Denning and Ryan was cast in a minor, but important role as a boxing "ringer". He had his first credited role, while making a lasting association with the director in which they would make several films together.
On March 11, 1939, he married Jessica Cadwalader. They had three children: Timothy (b. 1946); Cheyney (b. 1948), a research fellow at Oxford University and a professor of philosophy and law at the University of Oregon; and Lisa (b. 1951). They lived in The Dakota at 72nd and Central Park West in Manhattan and eventually sub-let the apartment to John Lennon and Yoko Ono.