Background: Although caregivers of patients with eating disorders usually experience a heavy caregiving burden, the effects of social support on caregivers of patients with eating disorders are unknown. This study aimed to investigate how social support for mothers who are caregivers of patients with an eating disorder improves the mothers’ mental status and, consequently, the symptoms and status of the patients. Methods: Fifty-seven pairs of participants were recruited from four family self-help groups and one university hospital in Japan.