Cronyn was the husband of actress Jessica Tandy, with whom he was presented with the Kennedy Center Honor in 1986 and National Medal of Arts in 1990.

[citation needed] His great-uncle, Benjamin Jr., was both a prominent citizen and early mayor of London, Ontario, but was later indicted for fraud and fled to Vermont.

During his tenure in London, he built a mansion called Oakwood, which currently serves as the head office of the Info-Tech Research Group.

After leaving Elmwood, Cronyn went to Ridley College in St. Catharines, and McGill University in Montreal, where he became a member of Kappa Alpha Society.

Early in life, Cronyn was an amateur featherweight boxer, having the skills to be nominated for Canada's 1932 Olympic Boxing team.

[citation needed] After graduating from Ridley College Cronyn attended McGill University, where he switched majors from pre-law to drama.

[citation needed] In 1934, the same year he joined The Lambs, he made his Broadway debut as a janitor in Hipper's Holiday and became known for his versatility, playing a number of different roles on stage.

[3] Cronyn starred with his second wife Jessica Tandy in a short-lived (1953–1954) radio series, The Marriage (based on their earlier Broadway play, The Fourposter), playing New York attorney Ben Marriott and his wife, former fashion buyer Liz, struggling with her switch to domestic life and their raising an awkward teenage daughter (future soap opera star Denise Alexander).

The series, which was the first situation comedy broadcast in color, premiered in July 1954 to "warm and enthusiastic reviews"; eight episodes were aired.

[4] The couple also appeared in many memorable dramatic stage, film and television outings, including The Seventh Cross (1944), The Green Years (1946), The Gin Game (1977), Honky Tonk Freeway (1981), The World According to Garp (1982), Cocoon (1985), the television film Foxfire (1987), *batteries not included (1987), Cocoon: The Return (1988), To Dance with the White Dog (1993) and Camilla (1994).

Cronyn and Tandy lived in the Bahamas, then at a lakeside estate in Pound Ridge, New York, and, finally, in Easton, Connecticut.