Born Mildred Linton in Ottumwa, Iowa, Morley lived there until she was thirteen years old. When she moved to Hollywood, she attendedHollywootd High School and later graduated from UCLA.

After working at the Pasadena Playhouse, she came to the attention of the director Clarence Brown, at a time when he had been looking for an actress to stand-in for Greta Garbo in screen tests. This led to a contract with MGM and roles in such films as Mata Hari (1931), Scarface (1932),The Phantom of Crestwood (1932), The Mask of Fu Manchu (1932), Arsene Lupin (1933) and Dinner at Eight (1933).

In 1934, Morley left MGM after arguments about her roles and her private life. Her first film after leaving MGM was Our Daily Bread (1934), directed by King Vidor. She continued to work as a freelance performer, and appeared in Michael Curtiz's Black Fury, and The Littlest Rebel with Shirley Temple. Without the support of a studio, her roles became less frequent, however she did play Mr. Collins' wife Charlotte Lucas in Pride and Prejudice (1940), which was produced by MGM. The film was critically well-received, but it did not advance her career, as a result, Morley turned her attention to stage plays.

In the early 1940s, she appeared in several plays on Broadway, including as Gerda in the original production of The Walrus and The Carpenter.

Her career came to an end in 1947, when she testified before the House Un-American Activities Committee and refused to answer questions about her alleged American Communist Party membership. She maintained her political activism for the rest of her life. In 1954, she ran unsuccessfully for Lieutenant Governor of New York on the American Labor Party ticket.

After being blacklisted in Hollywood by the studio bosses, she was never able to rebuild her acting career.

In the early 1970s, Karen Morley briefly resumed her acting career with guest roles in television series such as Kojak, Kung Fu, and Police Woman

In December 1999, at the age of 90, she appeared in the magazine Vanity Fair in an article about blacklist survivors.

Morley was married to director Charles Vidor from 1932 until 1943. They met on the set of Man About Town, in which Morley played the female lead, and Vidor was co-director. Vidor and Morley had a son, Michael Karoly, who was born in August 1933. Morley and Vidor were divorced in 1943, and later that year, she married the actor Lloyd Gough. They had one child together. They were married until Gough's death in 1984.

Morley lived in Santa Monica, California, during her later years. She died from pneumonia in Woodland Hills, California, at the age of 93, and was survived by two grandsons, a great-grandson, and a great-granddaughter. Source: Wikipedia