Suicidality is significantly more common in autistic adults than the general population, yet the factors that increase risk for suicidality among autistic adults remain largely unknown. We identified characteristics associated with suicidal ideation and suicide attempts/self-inflicted injury in a U.S. national sample of Medicare-enrolled autistic adults. We conducted a case-control study of autistic adults aged 18-59 years (n = 21,792). Younger age, white race, depression disorders, and psychiatric healthcare utilization were associated with increased odds of suicidal ideation and suicide attempts. Co-occurring intellectual disability was associated with significantly greater odds of a suicide attempt, but lower odds of suicidal ideation. Findings underscore the need for improved methods to identify ideation prior to attempt among adults with autism and intellectual disability.