To understand experiences of using second-generation advanced hybrid closed-loop (AHCL) therapy in adolescents and young adults with chronically elevated glucose levels who were previously using multiple daily injections (MDI) therapy. Semi-structured interviews with participants aged 13-25 years, on AHCL therapy for 3 months as part of a single-arm prospective study. Key inclusions: HbA1c ≥69 mmol/mol (8.5%); diabetes duration ≥1 year; and using MDI therapy prior to the study. Qualitative content analysis was used to identify themes and subthemes. Interviews were conducted among 14 participants with mean age 19.4 ± 4.3 years and mean baseline HbA1c 90 ± 25 mmol/mol (10.4 ± 4.5%). Three themes were identified: (1) substantially improved glucose levels improved perceptions of overall health; (2) features of AHCL aid in adoption and ongoing self-management; and (3) burden of care was reduced through automation of insulin delivery. Overall, there were positive impacts on physical, mental and social well-being. Participants were willing to overlook minor frustrations with AHCL because of the vast benefits that they had experienced. Four participants reported transient pseudo-hypoglycaemia: symptoms of hypoglycaemia when objectively measured glucose was in the clinically recommended range (3.9-10 mmol/L, 70-180 mg/dL). Transition to AHCL therapy positively impacted diabetes management in adolescents and youth with chronically elevated glucose levels. It appears to create a window of opportunity in which youth may re-engage with diabetes management. Pseudo-hypoglycaemia can occur during the transition to AHCL. This could be a barrier to AHCL uptake and is likely to require individualised support.