Her Sister's Secret is a 1946 American drama film directed by Edgar G. Ulmer and starring Nancy Coleman, Margaret Lindsay, Phillip Reed, and Regis Toomey. It centers around a woman who falls in love with a soldier. Believing she has been abandoned, she gives her baby to her married sister. The picture was produced and distributed by Producers Releasing Corporation. The screenplay was by Anne Green from the novel Dark Angel by Gina Kaus.

Edgar Georg Ulmer was a Jewish-Moravian, Austrian-American film director who mainly worked on Hollywood B movies and other low-budget productions, eventually earning the epithet 'The King of PRC', due to his extremely prolific output for the Poverty Row studio. His stylish and eccentric works came to be appreciated by auteur theory-espousing film critics in the years following his retirement. Ulmer's most famous productions include the horror film The Black Cat (1934) and the film noir Detour (1945).