AimsEvidence is lacking on whether diabetes duration is associated with type 1 diabetes (T1D) self‐management during late adolescence before transfer from paediatric to adult care. We examined associations of diabetes duration with dimensions of perceived comfort with diabetes self‐management (self‐efficacy, transition readiness, diabetes distress) and glycaemic control in late adolescence.MethodsUsing a cross‐sectional design, we conducted a secondary analysis of baseline data of adolescents (ages 16‐17 years) with T1D followed at paediatric diabetes academic hospitals in Montreal and enrolled in the Group Education Trial to Improve Transition (GET‐IT‐T1D). Participants completed validated questionnaires on self‐efficacy (Self‐Efficacy for Diabetes Self‐Management Measure [SEDM], score 1 to 10), diabetes distress and transition readiness, as well as a haemoglobin (HbA1c) capillary blood test. Our primary outcome was self‐efficacy. We examined associations of diabetes duration with self‐efficacy, diabetes distress, transition readiness and HbA1c using linear and logistic regression models adjusted for sex, socioeconomic status, insulin pump use, glucose sensor use, and psychiatric comorbidity.ResultsOf 203 adolescents with T1D, mean diabetes duration (SD) was 7.57 (4.44) years. Mean SEDM score was 6.83 (SD 1.62). Diabetes duration was not associated with self‐efficacy, diabetes distress or transition readiness. Each additional year of diabetes duration was associated with 0.11% (95% CI, 0.05 to 0.16) higher HbA1c.ConclusionsWhereas diabetes duration is not associated with dimensions of perceived comfort with diabetes self‐management, adolescents with longer diabetes duration are at risk for higher HbA1c and may need additional support to improve glycaemic control before transition to adult care.