While there is emerging evidence on the prevalence of physical and mental health conditions among autistic adults, less is known about this population's needs during older adulthood (aged 65+). We conducted a cross-sectional retrospective cohort study of 2016-2017 Medicare data to compare the prevalence of physical and mental health conditions in a national sample of autistic older adults (N = 4685) to a matched population comparison (N = 46,850) cohort. Autistic older adults had significantly greater odds of nearly all physical health conditions including epilepsy (odds ratio = 18.9; 95% confidence interval = 17.2-20.7), Parkinson's disease (odds ratio = 6.1; 95% confidence interval = 5.3-7.0), and gastrointestinal conditions (odds ratio = 5.2; 95% confidence interval = 4.9-5.5). Most mental health conditions were more common among autistic older adults, including schizophrenia and psychotic disorders (odds ratio = 25.3; 95% confidence interval = 22.4-28.7), attention deficit disorders (odds ratio = 24.4; 95% confidence interval = 16.2-31.0), personality disorders (odds ratio = 24.1; 95% confidence interval = 17.8-32.5), and suicidality or self-inflicted injury (odds ratio = 11.1; 95% confidence interval = 8.9-13.8). Health conditions commonly associated with advanced age in the general population (e.g. osteoporosis, cognitive disorders, heart disease, cancer, cerebrovascular disease, osteoarthritis) were also significantly more common among autistic older adults. By highlighting the significant physical and mental health needs for which autistic older adults require care, our findings can inform healthcare systems, healthcare providers, and public health initiatives seeking to promote well-being in this growing population.