Objective: Obesity is a major public health concern internationally; this study aims to identify the prevalence of obesity among mentally disabled children and to assess their nutritional status. Subjects and methods: This is a descriptive cross sectional study that was conducted at all forty special education institutes in Khartoum state; Sudan. The study included 290 children. Obesity is defined as = 95th percentile of the sex-specific body mass index for age growth charts. Questionnaire was developed including: general information, intelligence quotient and 24 hour dietary recall method. Results: The study showed that the prevalence of the obesity in mentally disabled children is 28.3%. Based on the Recommended Dietary Allowance (RDA) cutoff levels, 54.8% of the study group had unacceptable high intake of protein (= 120% of RDA), only 21% had acceptable (< 75-100% of RDA) caloric intake. The calcium intake of the children was under the recommended values. The prevalence of the obesity was significantly associated with large family size and poor nutritional knowledge of the mothers. Conclusion: The prevalence of malnutrition is high among mentally disabled children. Nutrition care should be incorporated in a multi-dimensional care for such group of children.