This study compared Medicaid service utilization and expenditures among adolescents with autism spectrum disorder (ASD) to adolescents with intellectual disability (ID) as they aged into adulthood. Medicaid Analytic eXtract (MAX) data was used to identify a national cohort. Winsorization was utilized to control for expenditure outliers. A greater proportion of adolescents with ASD utilized most services. Decreases in the use of key services, including psychiatric outpatient services, were observed for both groups. Changes in medical services, such as increases in inpatient and long term care services, among the ASD cohort suggest medical needs of adolescents with ASD change as they age. Information remains lacking on changing ASD symptom presentation during the transition to adolescence.