Background The transition of young adults with type 1 diabetes from pediatric to adult health care usually takes place at the end of secondary schooling, at a time when they are also experiencing multiple life transitions. Diabetes self-care management will often be of low priority for young people as they adjust to new routines involved with further study, employment and relationships. Failure to transition successfully may result in loss to medical follow-up, deterioration in diabetes control and development of short and long term diabetes complications. Objectives The primary focus of this systematic review was to identify the best available evidence of factors that determine diabetes care outcomes for young adults with type 1 diabetes after transition from pediatric to adult health care services. Data synthesis Where data were available, it has been pooled and presented as a forest plot in the review results. Studies with textual data results or where synthesis is inappropriate are presented as a narrative summary. Results Forty-one studies that potentially met the criteria for inclusion in the review were identified by the search strategy, of which 13 met the inclusion criteria. Factors identified to assist transition in the review studies related to either structured or unstructured interventions. The results of this review demonstrate that when a structured program is in place to assist the transition from pediatric to adult diabetes services, young people are less likely to require hospitalization for acute diabetes complications and more likely to attend appointments at the adult diabetes service. Conclusions The evidence identified from this review is suggestive that a structured transition intervention employing a dedicated health professional to support and coordinate the process is more likely to prevent loss to follow-up, maintain clinic attendance, have a positive impact on diabetes control, reduce hospital admissions, and be a more cost effective and positive experience for patients than an unstructured or usual care model.