Group clinics are becoming popular as a new care model in diabetes care. This evidence synthesis, using realist review methodology, examined the role of group clinics in meeting the complex needs of young people living with diabetes. Following Realist And Meta-narrative Evidence Synthesis–Evolving Standards (RAMESES) quality standards, we conducted a systematic search across 10 databases. A total of 131 articles met inclusion criteria and were analyzed to develop theoretically informed explanations of how and why group clinics could work (or not) for young people with diabetes. Models of group-based care in the literature varied significantly and incorporated different degrees of clinical and educational content. Our analysis identified four overarching principles that can be applied in different contexts to drive sustained engagement of young people in group clinics: 1) emphasizing self-management as practical knowledge; 2) developing a sense of affinity between patients; 3) providing safe, developmentally appropriate care; and 4) balancing group and individual needs. Implementation of group clinics was not always straightforward; numerous adjustments to operational and clinical processes were required to establish and deliver high-quality care. Group clinics for young people with diabetes offer the potential to complement individualized care but are not a panacea and may generate as well as solve problems.