Background: Adults with intellectual and developmental disabilities want to be included in all aspects of community life, but social inclusion continues to be very limited. Method: We used a qualitative multiple case study to describe the experiences and perspectives of four older workers or retirees with intellectual and developmental disabilities aged 45 to 63 who each participated in a different socially inclusive community group. Results: Three themes emerged: finding a good match; support for participation; and the outcomes of participating in a mainstream community group. A good match included both the group's activity and the people in the group. Support came from family, disability service provider staff, and the members of their group. The person's own attitudes and abilities also supported their participation. Inclusion in mainstream community groups led to a sense of belonging and other beneficial outcomes. Conclusions: Adults with intellectual and developmental disabilities can successfully participate long term in mainstream community groups.