Objective: Literature shows that practicing physical activity improves the general health and quality of life of people with intellectual disabilities. However, there is little empirical research on the specific benefits physical activity provides and to what extent these benefits occur. The goal of this study was to examine the impact of perceptions of physical activity and the individualized support on each of eight quality of life-related domains and three higher-order quality of life factors. Method: The sample consisted of adults with intellectual disability (n = 529), their assigned professionals (n = 522), and a family member (n = 462). Most participants attended day and residential services, and we applied the Personal Outcomes Scale and the Support Needs and Strategies for Physical Activity Scale to all of them. Results: The structural model parameter estimation showed high values, especially for the factor of well-being. These data allowed us to confirm that perceptions of physical and individualized supports in the field of physical activity act as predictors of quality of life improvement. Conclusions: The results suggest that organizations devoted to enhancing personal outcomes should include physical activity in their programs, and revise both their own services and the use of physical activity resources available in the community.