BackgroundYoung people with diabetes experience poor clinical and psychosocial outcomes, and consider the health service ill-equipped in meeting their needs. Improvements, including alternative consulting approaches, are required to improve care quality and patient engagement. We examined how group-based, outpatient diabetes consultations might be delivered to support young people (16–25 years old) in socio-economically deprived, ethnically diverse settings.MethodsThis multi-method, comparative study recruited a total of 135 young people with diabetes across two implementation and two comparison sites (2017–2019). Informed by a ‘researcher-in-residence’ approach and complexity theory, we used a combination of methods: (a) 31 qualitative interviews with young people and staff and ethnographic observation in group and individual clinics, (b) quantitative analysis of sociodemographic, clinical, service use, and patient enablement data, and (c) micro-costing analysis.ResultsImplementation sites delivered 29 group consultations in total. Overall mean attendance per session was low, but a core group of young people attended repeatedly. They reported feeling better understood and supported, gaining new learning from peers and clinicians, and being better prepared to normalise diabetes self-care. Yet, there were also instances where peer comparison proved difficult to manage. Group consultations challenged deeply embedded ways of thinking about care provision and required staff to work flexibly to achieve local tailoring, sustain continuity, and safely manage complex interdependencies with other care processes. Set-up and delivery were time-consuming and required in-depth clinical and relational knowledge of patients. Facilitation by an experienced youth worker was instrumental. There was indication that economic value could derive from preventing at least one unscheduled consultation annually.ConclusionsGroup consulting can provide added value when tailored to meet local needs rather than following standardised approaches. This study illustrates the importance of adaptive capability and self-organisation when integrating new models of care, with young people as active partners in shaping service provision.Trial registrationISRCTN reference 27989430.