The current study examined the relations among components of a physical activity program, Special Olympics (SO), and the self-concepts (i.e., perceived physical competence, social acceptance, and general self-worth) and adaptive behaviors of individuals with developmental disabilities. This research can assist in the development of theoretical models of how physical activity programs can be implemented to effect psychological change. Participants consisted of a randomly selected group of 97 individuals with developmental disabilities, between 9 and 43 years of age, and their parents. Participants’ self-concepts and adaptive behaviors were measured both by direct interview and parental report. Examined program components consisted of the length of time affiliated to the organization, number of competitions attended, of hours spent in training, of sports, and of medals obtained. Multiple regression analyses suggest relations between specific components of SO and participants’ self-concepts and adaptive behaviors. These relations highlight the importance of competition and sport for individuals with developmental disabilities.