Born Gertrude Constance Samwell in India, Benson became the wife of actor Frank Benson in 1886. They had two children, Eric William (1887-1916) and Byrnhild Lucy (b. 1888). After F. R. Benson's affair with the actress Genevieve Smeek (d. 1927), the couple separated. However, they did not divorce, and Constance (who had become Lady Benson in 1916) attended her husband's funeral as his widow, in 1940.
Constance Benson worked in theatre for most of her career, but did appear in lead roles in four silent films, all of which were early film adaptations of William Shakespeare plays. She starred in film versions of Shakespeare's Richard III, Julius Caesar, Macbeth, and The Taming of the Shrew, all in 1911. During the First World War (in which her son, Eric was killed), Benson ran a canteen for soldiers in France.
In addition, Benson was the author of an autobiography, Mainly Players (1926); two novels, The Chimera (1928) and Cuckoo Oats (1929); and an acting manual.