Background: Reciprocal relationships exist between motor competencies, physical activity and self-concept. Aims: Using a structural equation model, this study examined whether these relationships also appear in children with intellectual disabilities, how they can be validly measured, and if there are differences between children with and without intellectual disabilities. Materials & Methods: Data from a cross-sectional research project involving 121 children with intellectual disabilities and 1721 without intellectual disabilities were analysed. Results: The results demonstrate that reciprocal relationships also apply to children with intellectual disabilities and can be elucidated if inverse items are omitted. Discussion: Children with intellectual disabilities have less developed motor competencies and are less physically active but have a higher general self-concept compared to children without intellectual disabilities. The sport-related ability self-concept of both groups is comparable. Conclusions: The results are broadly consistent with extant research and illustrate that the development of motor competencies, physical activity and self-concept in children with intellectual disabilities must be encouraged.