Beginning in 2010 the Affordable Care Act (ACA) allowed young adults (ages 19–25) to remain on their parents’ private health insurance plans, even if they were not full-time students. This study investigated the impact of the ACA on health insurance coverage for young adults with disabilities, comparing their experience with that of young adults without disabilities and that of a group of older adults (ages 26–34) with disabilities. We analyzed the periods 2006–09 and 2011–14, which were before and after implementation of the dependent coverage provision in the ACA, respectively. Coverage gains for older adults with disabilities were entirely attributable to changes in public insurance. Gains for young adults overall were driven by changes in private insurance. Both young adults with and without disabilities experienced a 4-percentage-point increase in private health insurance coverage between the two time periods, so the gap in private coverage between the two groups did not change significantly over time. Gains in coverage affected perhaps 2.9 million young adults overall and nearly 300,000 young adults with disabilities.