Dorothy's mother Mary began acting in order to support the family after her husband left. When they were old enough, Dorothy and Lillian were brought into their mother's act, and they also modeled. In 1912 they met Mary Pickford, and she got them work at the Biograph studios.
Dorothy and Lillian both debuted in D.W. Griffith's An Unseen Enemy. Dorothy would go on to star in over 100 short films and features, many of them with Lillian.
Overshadowed by her sister's popularity, Dorothy virtually retired from motion pictures when talkies came along. She moved to England, where she turned her attention to the stage. From 1930 until her death, she only appeared in five more movies, and one television movie. She did make several appearances in anthology television series in the early 1950s.
She was married to James Rennie (1890-1965), a Canadian-born actor who was her co-star in "Remodeling Her Husband" (filmed in 1920, it was sister Lillian's only movie as director). They were married in 1920 in a double ceremony with actress Constance Talmadge and businessman John Piagoglou and were divorced in 1935.