Allyn Joslyn was born in Milford, Pennsylvania, the son of a mining engineer. On stage from age 17, Joslyn scored as a leading man in such Broadway productions as "Boy Meets Girl" (1936) and "Arsenic and Old Lace" (1941), appearing in the latter as beleaguered theatrical critic Mortimer Brewster. However, Hollywood didn't see Joslyn as a leading type. Thus, he spent most of his film career playing obnoxious reporters, weaklings, and formless "other men" who never got the girl, while stars such as James Cagney and Cary Grant took the roles he originated on Broadway.