Background: Due to lack of detailed standards of sexual maturity in individuals with Intellectual, sensory and motor disability in Iran and the importance of timing of onset of puberty in these individuals, a study is necessary. By knowing the onset of puberty, physiologic and behavioral changes can be traced in these people, as well as the potential impact of the puberty on the underlying disease can be considered. The aim of the study was to investigate of sexual maturation among boys of special schools of Tehran. Materials and Methods: Cross-sectional study was performed on children and adolescents male students in special school in Tehran at 2013. A random, multistage sample 0f 895 boy students of special schools was taken from 25 special schools in five districts of Tehran city. In this study, symptoms and stages of puberty were identified. Pubertal stages were assessed by visual inspection and palpation based on the rating scales of Tanner. In addition, demographic data such as age, height, weight were collected. Then the data were analyzed and mean age of onset of puberty was determined. Results: The mean age of onset of puberty in boys (Genitalia stage 2) was 13.12 ± 1.84 years and sexual maturation was completed at 16.57 ± 1.34 years. The average height at the onset of puberty (Genitalia stage 2) was 151.1 ± 9.91 cm and the average weight was 48.47 ± 10.14kg. The mean BMI for puberty onset was 20.89 ± 5.43. Conclusion: In our study, the mean age of puberty onset in boys with disabilities was 13.12 ± 1.84 years. Compared to the data from healthy boys, our findings indicate that the mean age of pubertal onset in boys with disabilities in special school is higher than that of their healthy counterparts.