None of the approved immunomodulatory drugs in adults Multiple Sclerosis (MS) patients have been officially approved for the pediatric patients and are currently used off-label in this population. In this study, we evaluated the effectiveness and tolerability of intramuscular interferon beta1-a (Avonex®) and subcutaneously injected interferon beta1-b (Betaferon®) in children with definite relapsing-remitting MS (RRMS). Thirteen patients aged younger than 16, who were recently diagnosed with definite RRMS according to the McDonaldʹs criteria, were enrolled in this study. Six patients were treated with Avonex® 30 μg, intramuscularly every week, and seven patients were treated with Betaferon® 250 μg, subcutaneously every other day. All patients were treated with adult doses; initially interferon-beta was prescribed with half dose, and it was increased to full adult dose steadily. Eleven girls and two boys, mean (SD) age of 14.7 (1.9) years, were studied. Following nine months of using interferon-beta, nine patients (69.2%) had no relapses and the remaining four, experienced only one relapse. The mean EDSS score was decreased significantly after the study period. The present study provides reasonable data for the use of interferon-beta in Pediatric MS due to lack of short-term complications and safety. Studies with larger sample size and longer follow up duration are required to shed light on the long term impact of the interferon-beta therapy in children.