Background: Overweight and obesity in children with intellectual disabilities may be a major health threat. The purpose of this study was to examine the prevalence of overweight and obesity in Korean children with intellectual disabilities aged 7-18 years who did not have specific genetic syndromes or physical disabilities. Materials and methods: Participants were 2,404 children with intellectual disabilities aged 7-18 years attending thirteen special schools in Korea. Data from school health records were analysed using SAS (version 9.2). The differences between boys and girls were assessed for children's height and weight using t-tests and for children's age and weight status, such as using Chi-Square ([chi][squared]) test. The relationships between children's weight status, age and gender were reassessed using Chi-Square ([chi][squared]) test, and strengths of the relationships were measured using Gamma coefficient. Results: Approximately one-quarter of children with intellectual disabilities were either overweight or obese. Children's gender was significantly associated with their weight status, such that overweight and obesity were more prevalent in girls than in boys, specifically girls aged 15-18 years. There was a positive relationship between age and the prevalence of overweight and obesity in children for both boys and girls. Conclusions: The high rates of overweight and obesity in children with intellectual disabilities highlight the need for interventions to help children achieve healthy weight. Before conducting weight management interventions, identifying risk factors that influence weight status in children with intellectual disabilities is an important step. (Contains 2 tables and 1 figure.)