Retroperitoneal lumbar hernias are a rare entity. Atraumatic posterior perirenal hernias are an exceptionally rare form of retroperitoneal lumbar hernias. Because of their infrequency, there are no standardized methods of surgical care for the treatment of atraumatic (primary spontaneous) posterior perirenal hernias. This report documents the finding and management of an atraumatic posterior perirenal lumbar hernia in a 69-year-old female.