Racial/ethnic disparities in access to diagnostic services are pervasive for autistic children. However, a few studies have examined racial/ethnic health disparities among autistic adults, who commonly experience higher rates of health conditions than non-autistic adults. We aimed at examining the intersection of autism and race/ethnicity in association with psychiatric and medical diagnoses. The study population included adult members of Kaiser Permanente Northern California enrolled from 2008 to 2012. We ascertained 1507 adults who had an autism diagnosis documented in their electronic medical records. We sampled a matched control group of adults without an autism diagnosis (N = 15,070) at a 10:1 ratio. Our sample was 46% White, 17% Hispanic, 16% Asian, 7% Black, and 14% other race/ethnicity. We compared health diagnoses (a) between autistic and non-autistic adults within strata of race/ethnicity and (b) across race/ethnicity within strata of autistic and non-autistic adults. Lastly, we examined the interaction between autism and race/ethnicity on both multiplicative and additive scales. Autistic adults were more likely to be diagnosed with most medical and psychiatric conditions compared with their non-autistic counterparts of the same race/ethnicity. Among autistic adults, Black, Hispanic, and Asian adults were less likely to be diagnosed with psychiatric conditions and Black and Hispanic autistic adults were more likely to be diagnosed with obesity than their White counterparts. In interaction models, we found that adults who were Black and autistic were disproportionately less likely to be diagnosed with psychiatric conditions and autoimmune disease and more likely to be diagnosed with hypertension than expected. Health vulnerabilities may be compounded at the intersection of autism and race/ethnicity. Future research should continue to apply an intersectional lens toward understanding and addressing these disparities. Our findings likely underestimate the health disparities that exist in uninsured autistic adults and those living in other parts of the United States. Very few studies have looked at how the combination of a person’s autistic and racial/ethnic identities affects their health in adulthood. Dual experiences of ableism and structural racism may have a larger negative effect on the health of autistic people of color than either one experience alone. It is important to identify potential health disparities so that they can be addressed. We wanted to understand whether autistic adults of color were more likely to be diagnosed with medical and psychiatric conditions than non-autistic and/or White peers. We studied a diverse group of 1507 autistic adults and 15,070 non-autistic adults who all received health care from the same large, health plan in California. We examined electronic health records to determine whether diagnoses of health conditions differed by autism status and race/ethnicity. We then looked at whether autistic people of color were disproportionately diagnosed with these conditions compared with other groups. Within every racial/ethnic group, autistic adults were more likely than non-autistic adults to be diagnosed with most medical and psychiatric conditions. Among the autistic group, Black, Hispanic, and Asian adults were less likely to be diagnosed with psychiatric conditions compared with White adults. We saw similar differences in psychiatric diagnoses by race/ethnicity among non-autistic adults. Further, the diagnostic patterns among adults who were autistic and Black suggested that this group may experience unique difficulties receiving mental health and autoimmune diagnoses. They also may be at a higher risk of hypertension. Previous studies have found racial/ethnic disparities in both mental health and access to health care among autistic children. This study suggests that racial/ethnic disparities, especially in mental health care, may also exist among autistic adults. As a broad social label, race/ethnicity does not tell us much about people’s lived experiences. Future studies should replace race/ethnicity with more useful measures of our social environment, including economic opportunity and experiences of structural racism. In addition, health records may imperfectly represent the actual occurrence of health conditions. For example, we cannot tell from this study whether autistic people of color actually experience fewer psychiatric problems, are less likely to visit the doctor, or are more likely to have their problems missed by doctors. Lastly, because our findings are from an insured population, we have likely underestimated the health disparities that exist among autistic adults who do not have consistent insurance coverage or health care access. We hope this study highlights the need for greater attention to the unique health risks at the intersection of autism and race/ethnicity in adults. Through more research and advocacy, we can increase awareness and understanding of these potential health disparities. This will lead to changes that promote more equal access to health care and greater well-being among autistic people of color.