We propose a justice-based partnership between employees and family members as a means to create services and support systems for people with intellectual disability, enhancing quality of life indicators. More specifically, we examine the links from mutual intergroup justice to three outcomes reported by family members: satisfaction with the center, service quality delivered by employees, and performance focused on the quality of life of people with intellectual disability. We used data from 111 centers. In each center, a group of family members (n = 845) and a group of employees (n = 914) participated. Multilevel modeling revealed that mutual intergroup justice (between employees and family members) has a positive effect on satisfaction with the center, perceptions of functional and relational service quality, and performance based on quality of life.