Fletcher appeared on the stage in 1927 and made his Broadway debut in 1929. Hollywood and sound films soon beckoned. He made his first film in 1928, S.O.S. Fletcher co-starred in Warner Brothers' 1931 film Svengali with legendary actor John Barrymore, whose daughter Diana, Fletcher would marry a decade later. He had a brief, but notable appearance in The Mummy (1932) as the assistant gone mad. In 1943, he abandoned films for the theatre and television. He wrote and acted in the critically successful 1965 play The Bernard Shaw Story.
His first two wives were actresses. He was married to Helen Chandler from 1935 to 1940 and Diana Barrymore from 1942 to 1946. Both marriages ended in divorce. In 1950 he married Susan Robinson and had 3 children. In 1970 he married Lael Tucker Wertenbaker and remained with her until his death in 1988.