Transition from pediatric to adult health care systems presents unique challenges for adolescents with autism spectrum disorder who often have complex medical and mental health needs. Without a coordinated transition plan, pediatric providers often continue to provide care to young adults with autism spectrum disorder beyond the scope of their medical training. Adult providers may be unwilling and untrained to accept care for young adults with autism spectrum disorder. This quality improvement study identified baseline transition-related practices within a pediatric medical home practice and developed a model to promote transition to adult heath care for patients with autism spectrum disorder. Participants were 251 patients with autism spectrum disorder aged 12–21 years. Baseline data revealed limited and inconsistent communication directed to patients and families regarding transition. An evidence-based and replicable transition checklist, templated documentation, and resources geared to patients aged 12–21 years were developed. While improvement was noted in number of visits addressing transition, medical providers skipped or deferred transition discussion in approximately half of well visits for targeted patients. Challenges in implementing the transition process included finding time to discuss transition-related issues with patients/families, preference of medical providers to defer to social work to address transition, and difficulty identifying adult providers with whom to collaborate regarding care needs. Lay abstract As adolescents become adults, they typically change from seeing a pediatric health care provider to seeing a health care provider who specializes in working with adults. Adolescents with autism spectrum disorder may have more difficulty finding an adult health care provider who is trained to address the varied needs and medical and mental health issues that often are seen with autism spectrum disorder. Without careful planning for transition to adult health care, patients may continue to be seen by pediatric providers who may not be familiar with adult health needs. This quality improvement project focused on improving transition to adult health care by creating varied supports for the patient, family, and the health care team and putting them into action within a pediatric medical practice that serves over 250 adolescent and young adult patients with autism spectrum disorder. Before the supports were put into place, patients and families received limited and inconsistent communication to help them with transition. While the supports helped increase the amount and quality of help patients and families received, medical providers skipped or put off transition discussion in approximately half of well visits for targeted patients. Challenges in implementing the transition process included finding time to discuss transition-related issues with patients/families, preference of medical providers to have social workers discuss transition, and difficulty identifying adult health care providers for patients. This suggests more work is needed to both train and partner with patients, families, and health staff to promote smooth and positive health transitions.