This study estimated compliance with American Academy of Pediatrics (AAP) guidelines for well-child care and the association between compliance and age at diagnosis in a national sample of Medicaid-enrolled children with autism (N = 1,475). Mixed effects linear regression was used to assess the relationship between compliance and age at diagnosis. Mean age at diagnosis was 37.4 (SD 8.4) months, and mean compliance was 55% (SD 33 %). Children whose care was compliant with AAP guidelines were diagnosed 1.6 months earlier than children who received no well-child care. Findings support that the timely receipt of well-child care may contribute to earlier detection. Additional research on the contribution of compliance, well-child visit components and provider characteristics on the timely diagnosis of autism is needed.