IMPORTANCE Obesity reportedly increases the risk of pediatric multiple sclerosis (MS), but little is known about its association with disease course. OBJECTIVE To investigate the association of obesity with pediatric MS risk and with first-line therapy response among children with MS. DESIGN, SETTING, AND PARTICIPANTS This single-center retrospective study used the medical records and database at the Center for MS in Childhood and Adolescence, Göttingen, Germany. The study included 453 patients with relapsing-remitting pediatric MS and body mass index (BMI) measurement taken within 6 months of diagnosis.