This study examined the relationship between imitation, motor movement, and language skill in 70 children with developmental disabilities. Four primary research questions were addressed: 1) What are the imitation, motor movement, and language profiles of young children with developmental disabilities?; 2) What is the relationship between imitation skill, motor movement, and language skill?; 3) What is the relationship between imitation, motor movement, and language skill, when accounting for reported spoken imitation skills?; and 4) Does motor movement skill moderate the relationship between imitation and language skill? Standardized direct assessments, parent report, and observational kinematic motion capturing was used to measure the participants’ skill repertoire. In addition to replicating past research supporting the imitation-language relationship, the results of this study provided new evidence that motor movement is a significant moderator of this relationship. Furthermore, it was shown that the moderating effect of motor movement differs by developmental diagnosis, specifically for children with Autism Spectrum Disorder (ASD) and Down syndrome (DS).