Background: Parents often face many barriers when taking care of their offspring with disabilities. In childhood, support needs vary with families of children with Down syndrome often reporting less caregiving challenges. However, it is unclear whether support needs vary in adulthood. This study compared parents of adults with Down syndrome (DS), autism spectrum disorder (ASD) and cerebral palsy (CP) regarding support needs of their offspring with intellectual and developmental disabilities (IDD) and their families. Method: Data were collected via a national survey in the United States with 189 parents of adults with IDD. Results: Across the quantitative and qualitative analyses, parents of adults with DS (versus CP and ASD) reported significantly greater recreational, natural supports, more formal services and less future planning barriers. Conclusion: The results indicate that the DS advantage may persist in adulthood regarding support needs. More research is needed to understand different types of support needs.