Farmer was born in Seattle, Washington. She began acting in stage productions while she was a student at the University of Washington. When she graduated, she began performing in stock theatre. She later signed a contract with Paramount Pictures in 1936.
Farmer's first movie was Too Many Parents (1936). That was followed by a lead role in the musical western Rhythm on the Range (also 1936).
Farmer was unhappy with the opportunities given to her by the studio. She returned to stock theater in 1937. She was cast in the original Broadway production of Clifford Odets' Golden Boy.