Type 1 diabetes requires complex day-to-day management to reduce the risk of severe medical complications. Problems with adherence and glycemic control are especially common in adolescence. During this time, the primary responsibility for diabetes management shifts from parent to child. This may be problematic if the transition of responsibility occurs too early or too quickly, or if parents and youths disagree on the division of responsibilities. The present study employed a longitudinal approach using multilevel growth curve modeling to examine characteristics of successful parent-youth transition of responsibility for diabetes management. The first study aim was to characterize developmental trajectories in levels of youth autonomous responsibility and in parent-youth discrepancies about responsibility for diabetes management. The second aim was to examine how trajectories of youth responsibility levels and parent-youth discrepancies were related to trajectories of diabetes regimen adherence and glycemic control. The third aim was to examine whether family characteristics predicted responsibility levels and parent-youth discrepancies. At four times over two years, 87 youths with type 1 diabetes (10 to 16 years old at study entry) and their parents reported on the division of diabetes management responsibilities, and provided assessments of adherence. Glycemic control was indexed by laboratory measures of HbA1c taken during regular doctor visits. Characteristics of family functioning were assessed at study entry. Results showed that youths' levels of responsibility for diabetes management increased with age. Parent-youth discrepancies showed no consistent developmental trend; youths' perceptions of their responsibility exceeded parents' perceptions across all ages. However, trajectories of youth responsibility levels and of parent-youth discrepancies were diverse across individual families. Higher discrepancies, but not responsibility levels, were related to worse adherence and glycemic control at study entry. Moreover, an increase in discrepancies over the study period, but not change in responsibility levels, was related to worsening in adherence over time. Families with favorable communication patterns and little home chaos showed less discrepancy at study entry. The findings highlight the importance of understanding the successful transition of diabetes self-care responsibility during adolescence as a dynamic, interactive process. This may facilitate the development of family interventions to improve diabetes care in adolescence.