The Pediatric onset multiple sclerosis (POMS) prevalence is increasing worldwide accounting for around 3 to 10% of MS cases. The risk of POMS is supposed to reflect a complex interaction between environmental and genetic risk factors that may occur during the childhood, adolescent, or post-pubertal years.The present study aimed at estimating the prevalence of POMS and assessing the epidemiology of familial recurrence of POMS in Tehran.A retrospective population based cross-sectional study was designed from 1999 to 2017. The baseline characteristic information was collected from MS patient's ≤18 years old (y/o). Pearson's chi-square test and logistic regression were used to analyze the relationship among variables and estimate the odds ratio (OR) via SPSS software, version 23.A total of 1937 POMS patients (77.80% female and 22.20% male patients) participated in the study. The point prevalence of POMS was 16.20 per 100,000 populations in 2017. Mean age at disease onset was 15.96 ± 2.28 y/o. The female to male ratio was 2.02:1 in pre-pubertal cases (3-12 y/o), but it increased to 3.69:1 in 13-18 y/o age groups (P value = 0.001, OR = 1.82; 95% CI = 1.27-2.26). There were 288 (14.9%) cases with positive familial history of MS. The strongest association between MS risk and positive familial history was observed in second degree relatives who presented MS (P value = 0.046, OR = 1.74; 95%CI = 1.01-3.01). A significant association was observed among maternal second degree relatives with POMS (P value = 0.018, OR = 2.27; 95%CI = 1.15-4.47).In comparison to other large studies, the prevalence of POMS was high in the data collected from Tehran. POMS risk is higher among females and the sex ratio increases after puberty. We found a significant association between POMS risk and familial history in maternal second degree relatives. Further studies of POMS epidemiology might yield greater understanding of the natural history of this disease.