Young people with type 1 diabetes mellitus (T1DM) transition from paediatric to adult services when they reach late adolescence. This can be a risky period for young people, and it has been associated with a deterioration in glycaemic control and disengagement from diabetes services. This review aimed to identify current interventions addressing the following questions: What adolescents with T1DM healthcare transition interventions have been evaluated? What are the underlying theories and components of these interventions? What outcomes have been considered in these evaluations? Databases, trial registries and other sources were searched using the population and intervention keywords. Studies were included if they explicitly reported a transition intervention targeting young people aged 10–25 years. Studies were critically apprised, and data were extracted. Both tabular and narrative data synthesis were used. The review included 22 studies. Most interventions were service‐oriented, with little use of theory. The interventions included transition planning, service coordination, pre‐transition education, transition clinics, prompting strategies and other less frequent components. Most studies reported metabolic outcomes, with limited data on psychological outcomes such as diabetes adaptation, acceptance and self‐management activation. It is inconsistent how each outcome was defined, measured or reported. Consequently, effective theory‐based interventional transition models are yet to be identified.