Background and Objectives: Many adults with autism spectrum disorders require lifelong reliance on caregiver support. As these caregivers age and experience health challenges, social support can be critical. This study seeks to understand if caregiver health moderates the relationship between informal social support and caregiver burden.; Research Design and Methods: A total of 320 parents (age 50+ years) of adult children diagnosed with ASD were recruited from autism organizations and support groups and completed a web-based survey. Separate moderation analyses were used to determine if caregiver health was moderating the relationship between informal social support and composite caregiver burden, as well as the separate domains of developmental, time dependence, emotional burden, and impact of caregiving on finances. For each analysis, perceptions of available informal social support were the independent variable, composite and domains of caregiver burden were dependent variables, and parents' self-reported general health was the moderating variable.; Results: Caregiver health had a statistically significant moderating effect when predicting the relationships between informal social support and composite caregiver burden, as well as time dependence burden and impact of caregiving on finances.; Discussion and Implications: Increased attention should be focused on supporting the current and future needs of both aging caregivers and their adult children with ASD. Future research on the dynamics of social support, health, and burden is also urgently needed to address the growing number of aging caregivers of adults diagnosed with ASD.