Autistic adults often experience barriers to healthcare that can cause their healthcare service use to be unique from other populations. We conducted a systematic review to gather the most recent evidence about how often autistic adults use five important healthcare services (the emergency department, hospitalization, outpatient mental health, preventive services, and primary care) compared to populations of non-autistic adults. We searched six electronic research databases for articles. Our search strategy identified N = 2964 unique articles. Ultimately, we included N = 16 articles in our review. Most included studies (N = 13) were high-quality level 3a studies that compared autistic adults' service use to a non-autistic population comparison group (N = 11), and examined emergency department use (N = 12). Autistic adults most often had equal or higher use of services than population comparison groups across all healthcare services we examined. Although autistic adults had greater use of primary care and preventive services than comparison groups, frequent emergency department visits and hospitalizations may reflect that these services are not adequately meeting autistic adults' needs. Future research should identify targets for improving autistic adults' access to and use of primary care and preventive services, which may ultimately reduce frequent use of the emergency department and hospitalizations.