Many of the nearly six million autistic adolescents and adults in the United States require support to navigate daily life. Family members often provide the first line of support for autistic youth by providing care and coordinating services. Although considerable research has examined the perspectives of family members caring for young autistic children, comparatively less has focused on those caring for transition-age youth who often struggle to access needed services as they leave child-serving systems of care. This study examined caregiver-reported barriers to service for 174 adolescents and young adults on the spectrum (ages 16–30) and the association between such barriers and unmet service needs. Exploratory factor analysis suggested two service barrier domains: access (e.g., cost) and quality (e.g., providers not trained). Regression models indicated that caregivers whose youth were diagnosed at older ages perceived both greater access and quality barriers. Male caregivers reported fewer access barriers, and those who perceived greater caregiver burdens (daily life disruptions, financial difficulties, and worries) reported more access barriers. Caregivers whose youth lived with them reported fewer quality barriers. Greater access–but not quality–service barriers predicted greater unmet service needs. Findings have implications for service delivery to autistic youth and specific directions for future research. Lay Abstract Prior studies have described the roadblocks, or barriers, to needed services experienced by families with young autistic children, but less research has focused on those faced by autistic adolescents and young adults. In this study, we wished to understand the barriers to service experienced by autistic adolescents and young adults and their families. We surveyed 174 caregivers of autistic youth between 16 to 30 years old. We found that caregivers who felt more caregiving burden had more difficulty accessing services for their youth. Specifically, caregivers who felt more strongly that their daily lives had been disrupted, felt more financial strain, and worried more about their youth well-being experienced more roadblocks to getting services for the youth. Male caregivers also reported fewer difficulties related to service access. Importantly, the older the youth was when they had been diagnosed with autism, the more service barriers their caregivers reported. We did not see any differences in the level of barriers experienced by youth who lived in urban versus suburban settings, or between white and non-white families. However, when youth lived with their caregivers (rather than, for example, in a group home), fewer quality-related barriers to services were reported. Finally, greater access (but not quality) barriers were linked to youth having more unmet service needs. These findings can help to reduce the barriers to service experienced by autistic adolescents and young adults and their families.