Adolescents with type 1 diabetes struggle with glycemic control with decline further exacerbated by transfer from pediatric to adult care. The purpose of this systematic review/meta-analysis was to examine which components of transition programs are effective in improving outcomes following transfer. We searched six databases for studies that assessed the efficacy of a transition program on diabetes outcomes. Studies reporting hemoglobin A1c (HbA1c) or its change for the intervention versus control group pretransition and posttransition were pooled using a random effects meta-analysis model. Of 4,689 studies identified, 18 (1 randomized control trial, 6 quasi-experimental, 1 prospective, and 10 retrospective cohort) met inclusion criteria. Findings represent data from 3,382 youth with type 1 diabetes (52% male, age 16-23 years) undergoing transition. Programs varied and included transition coordinators (n = 7), transition clinics (n = 10), and group education meetings (n = 5). Average age of transfer was 17.7 years. All but one study reported improvement/maintenance of HbA1c posttransition. However, pooling data from four studies with a control group (418 youth), there were no differences in HbA1c at 12 months (-.11 [95% confidence interval: -.31, .08]). Of other outcomes studied (clinic attendance [n = 12], severe hypoglycemia [n = 8], and diabetic ketoacidosis [n = 7]), transition programs showed greatest consistency in reducing diabetic ketoacidosis episodes. Findings suggest that transition interventions may be effective in maintaining glycemic control and reducing diabetic ketoacidosis episodes posttransition. Further research is needed to determine which program types are most effective.