Aim: The aim of this study was to evaluate skeleto-dental abnormalities in 9-11-year-old school children, in Tehran, Iran. Materials and Methods: In this population-based cross-sectional descriptive study, a random cluster sampling was done among 19 school districts. A total of 1,429 socioeconomically and ethnically diverse Iranian schoolchildren, aged 9-11 years were studied. A brief questionnaire including background information such as gender and age was completed by the parents. Clinical examinations included the evaluation of sagittal and vertical skeletal relationship, Facial form (facial index), and the presence of significant asymmetry. Results: There were 758 males and 671 females with the mean age of 10 years±8 months. According to the sagittal skeletal relationship, the most prevalent type was convex (63%) that presenting the skeletal Cl II jaw relation; followed by straight (32.9%); and then concave (4.1%). In the vertical skeletal relationship, 73.9% of the children had an average facial relationship, 18.4 % had a long face pattern; and 7.8% had a short face pattern. Regarding facial form in the frontal view, the most common was the average form (79.3%); followed by narrow (14%); and broad (6.7%). The prevalence of significant facial asymmetry was 15.2%. Conclusion: The prevalence of dento-skeletal abnormalities were high. The majority of the Iranian schoolchildren, aged 9-11 years, had at least one dento-skeletal abnormality, even though it is commonly preventable.