This study examined hospitalizations in a large, all-payer, nationally representative sample of inpatient hospitalizations in the US and identified differences in rates of hospitalization for conditions by race and ethnicity in autistic adults. Conditions examined included mood disorders, epilepsy, schizophrenia, and ambulatory care sensitive conditions (ACSCs). Compared to white, non-Hispanic autistic adults, Black, Hispanic, Asian or Pacific Islander (API), and autistic adults of another race had lower prevalence of admission for a principal diagnosis of a mood disorder. Conversely, Black, Hispanic, API, and autistic adults of another race had higher odds of admission for epilepsy than white autistic adults. Black and Hispanic autistic adults were more likely to have schizophrenia as a principal diagnosis compared to white autistic adults, but only Black autistic adults had increased odds for admission for an ACSCs compared to white autistic adults. Differences in diagnosis prevalence among hospitalized autistic adults may suggest differential access to comprehensive outpatient care that could prevent such hospitalizations, while also pointing to concerns of differential validity of diagnostic tools and treatment approaches. Insurance policy and programs should prioritize optimizing outpatient care to ensure access to care and emphasize the need for equitable treatment.