Hart was born Catherine Conn in New Orleans on September 3, 1910. She was educated in Switzerland, the Sorbonne and the London School of Economics and studied acting in London at the Royal Academy of Dramatic Art. Returning to America, she apprenticed at the Bucks County Playhouse in Pennsylvania and, using the stage name Kitty Carlisle, made her Broadway debut in 1933 in the musical operetta Champagne Sec. Other Broadway credits included White Horse Inn 1933, Three Waltzes 1937, Walk With Music 1940, The Rape of Lucretia 1948, Anniversary Waltz 1954 and On Your Toes 1983, replacing Dina Merrill.
Baby Boomers remember Kitty Carlisle for her years as a panelist on TV's To Tell the Truth beginning in 1956, in which the fashionable actress was a glamorous presence. By then, she had been married for 10 years to playwright Moss Hart, whom she met at the Bucks County Playhouse. They had two children, Catherine and Christopher, before the playwright's death in 1961.
An operatically trained singer, Hart made her Metropolitan Opera debut in 1966 in Die Fledermaus. She served as chairperson of the New York State Council of the Arts from 1976-1996.
In recent years, Hart began performing in small cabaret settings, where she shared songs and stories of the great men in musical theater she worked with over the years, including onetime flame George Gershwin, Irving Berlin, Kurt Weill, Oscar Hammerstein, Jerome Kern, Frederick Loewe and her late husband. Hart celebrated her 96th birthday last September by appearing at Feinstein's at the Regency.