Background: The National Institute for Health and Care Excellence recommends that every locality has a ‘Specialist Autism Team’: an specialist autism, community-based, multidisciplinary service that is responsible for developing, co-ordinating and delivering care and support. The National Institute for Health and Care Excellence recommended that this novel delivery model was evaluated. Objectives: The objectives were to identify services fulfilling the National Institute for Health and Care Excellence’s description of a Specialist Autism Team; to describe practitioner and user experiences; to investigate outcomes; to identify factors associated with these outcomes; and to estimate costs and investigate cost-effectiveness of these services. Design: During stage 1, desk-based research and a survey to identify Specialist Autism Teams were carried out. Stage 2 comprised a mixed-methods observational study of a cohort of Specialist Autism Team users, which was followed for up to 2 years from the assessment appointment. The cohort comprised users of a Specialist Autism Team not previously diagnosed with autism (the ‘Diagnosis and Support’ group) and those already diagnosed (the ‘Support-Only’ group). Stage 2 also involved a nested qualitative study of senior practitioners and an exploratory comparison of the Diagnosis and Support group with a cohort who accessed a service which only provided autism diagnostic assessments (‘Diagnosis-Only’ cohort). Setting: The setting in stage 2 was nine Specialist Autism Teams; three also provided a regional diagnostic assessment service (used to recruit the Diagnosis-Only cohort). Participants: There were 252 participants in the Specialist Autism Team cohort (Diagnosis and Support, n = 164; Support Only, n = 88) and 56 participants in the Diagnosis-Only cohort. Thirty-eight participants (across both cohorts) were recruited to the qualitative evaluation and 11 practitioners to the nested qualitative study. Main outcome measures: The World Health Organization Quality of Life assessment, abbreviated version (psychological domain) and the General Health Questionnaire (12-item version). Data sources: Self-reported outcomes, qualitative interviews with users and focus groups with practitioners.Results: A total of 18 Specialist Autism Teams were identified, all for autistic adults without learning disabilities. Services varied in their characteristics. The resources available, commissioner specifications and clinical opinion determined service design. Practitioners working in Specialist Autism Teams recruited to stage 2 reported year-on-year increases in referral rates without commensurate increases in funding. They called for an expansion of Specialist Autism Teams’ consultation/supervision function and resources for low-intensity, ongoing support. For the Specialist Autism Team cohort, there was evidence of prevention of deterioration in outcomes and positive benefit for the Diagnosis and Support group at the 1-year follow-up (T3). Users of services with more professions involved were likely to experience better outcomes; however, such services may not be considered cost-effective. Some service characteristics were not associated with outcomes, suggesting that different structural/ organisational models are acceptable. Findings suggest that one-to-one work for mental health problems was cost-effective and an episodic approach to delivering care plans was more cost-effective than managed care. Qualitative findings generally align with quantitative findings; however, users consistently connected a managed-care approach to supporting improvement in outcomes. Among the Diagnosis-Only cohort, no changes in mental health outcomes at T3 were observed. Findings from the interviews with individuals in the Diagnosis and Support group and Diagnosis-Only cohort suggest that extended psychoeducation post diagnosis has an impact on immediate and longer-term adjustment. Limitations: Sample size prohibited an investigation of the associations between some service characteristics and outcomes. Comparison of the Diagnosis-Only cohort and the Diagnosis and Support group was underpowered. The economic evaluation was limited by incomplete costs data. Conclusions: The study provides first evidence on the implementation of Specialist Autism Teams. There is some evidence of benefit for this model of care. Service characteristics that may affect outcomes, costs and cost-effectiveness were identified. Finding suggest that extended psychoeducation post diagnosis is a critical element of Specialist Autism Team provision. Future work: We recommend a comparative evaluation of Specialist Autism Teams with diagnosis-only provision, and an evaluation of models of providing consultation/supervision and low-intensity support. Funding: This project was funded by the National Institute for Health Research (NIHR) Health Services and Delivery Research programme and will be published in full in Health Services and Delivery Research; Vol. 8, No. 48. See the NIHR Journals Library website for further project information.