This research study tested an intervention, based on autonomous teams and the service co-creation approach, to improve the social inclusion and self-determination (as indicators of quality of life) of people with intellectual disability. Members of the autonomous teams (professionals, people with intellectual disability, and family members) cooperated to plan and carry out a project. A total of 72 autonomous teams participated (experimental condition). Each team designed its action plan to be implemented during eight weeks. Three measurement times were used: before the intervention (T1), four (T2) and eight (T3) weeks after the starting point. Family members (experimental group, N = 117; control group, N = 187) reported on the social inclusion and self-determination of their relative with intellectual disability. Scores in the control group remained stable over time, whereas scores in the experimental group changed significantly. Social inclusion increased (T2), and later stabilized (T3). By contrast, self-determination increased (T2), but this improvement was subsequently reduced (T3).