The objective of this study was to determine whether family members of patients with pediatric multiple sclerosis (MS) have an increased prevalence of autoimmune conditions compared with controls. Data collected during a pediatric MS case-control study of risk factors included information about various autoimmune diseases in family members. The frequency of these disorders was compared between cases and controls. There was an increased rate of autoimmune diseases among family members of pediatric MS cases compared with controls with first-degree history of MS excluded (OR = 2.27, 95% CI 1.71-3.01, p < 0.001). There was an increased rate of MS among second-degree relatives of pediatric MS cases compared with controls (OR = 3.47, 95% CI 1.36-8.86, p = 0.009). The OR for MS was 2.64 when restricted to maternal relatives and 6.37 when restricted to paternal relatives. The increased rates of autoimmune disorders, including thyroid disorders and MS among families of patients with pediatric MS, suggest shared genetic factors among families with children diagnosed with pediatric MS.