Marshall first acted on stage. Her film career began with a small role in Caesar and Cleopatra (1945), with Claude Rains and Vivien Leigh. Her exotic looks resulted in her being cast in "ethnic" roles, such as Asian women, including her role as the Chinese character Miss Taro, in the first James Bond film, Dr. No (1962). She also appeared in Those Magnificent Men in Their Flying Machines (1965) as the Countess Ponticelli, and made numerous television appearances. Her last film performance was in The Terrornauts in 1967.