This study was conducted to evaluate the BMI of the children with intellectual disability and the factors affecting their BMI. This descriptive and cross-sectional study was carried out between March 2016 and April 2016 in Turkey and consisted of 135 children. Children's anthropometric measurements were and their BMI values were calculated. Categorization of children by BMI percentile according to AAP reference values was performed. There was a significant difference between the BMI categories of the children (p < 0.05) and the education level of children's father (x2 = 8.960; p = 0.028), the degree of intellectual disability (x2 = 16.113; p = 0.008), the presence of other disabilities (x2 = 22.013; p = 0.000), type of disability (x2 = 21.359; p = 0.001), the nutrient intake (x2 = 38.935; p = 0.000) and the presence of nutritional problems (x2 = 7.687; p = 0.042). Father's education level, children's degree of disability, child's having presence of other disabilities, child's being dependent in the view of nutrient intake, and child's having nutritional problems were determined as factors affecting BMI.