Karen Morley was born Mildred Linton on December 12, 1909, in Ottumwa, Iowa. She was adopted by a well-to-do family who relocated to Los Angeles in the mid-1920s. Morley attended Hollywood High School and initially pursued a career in medicine at UCLA, but a theater class at Pasadena Playhouse redirected her ambitions.
After being signed by Fox Studios, Morley's big break came when producer Howard Hughes selected her to play the blonde moll in the 1932 crime epic, Scarface. She was subsequently put under contract by MGM and starred in several early 1930s films, including Mata Hari alongside Greta Garbo, Arsène Lupin with John Barrymore, and Dinner at Eight with Jean Harlow. Morley also worked with notable actors such as Lionel Barrymore, Wallace Beery, and Boris Karloff.
In 1934, Morley left MGM due to disagreements about her roles and personal life, including her desire to start a family and her marriage to director Charles Vidor. She continued to work as a freelance performer, appearing in King Vidor's Our Daily Bread, Michael Curtiz' Black Fury, and Pride and Prejudice.
In 1947, Morley's screen career came to a halt when she testified before the House Committee on Un-American Activities and refused to answer questions about her possible enrollment in the Communist Party. Following this, she continued to promote left-wing causes and married actor Lloyd Gough.
In 1954, Morley ran unsuccessfully as a New York lieutenant governor candidate for the American Labor Party. Morley passed away on March 8, 2003, at the Motion Picture Country House in Woodland Hills.