Objectives: Chronotype reflects individual circadian preferences and may influence metabolic regulation and daily functioning. This study aimed to investigate the association between chronotype and glycaemic control, assessed by HbA1c, as well as health-related quality of life in children and adolescents with type 1 diabetes mellitus. Methods: This cross-sectional study included 84 children and adolescents aged 8–18 years with type 1 diabetes of at least one year’s duration. Chronotype was assessed using the Munich Chronotype Questionnaire. Health-related quality of life was evaluated using age-appropriate versions of the Pediatric Quality of Life Inventory (PedsQL™). Glycaemic control was assessed using the mean HbA1c value from the most recent three months. Results: Chronotype distribution was 19.0 % morning, 44.0 % intermediate, and 36.9 % evening. HbA1c levels differed significantly among chronotype groups (p=0.003), with higher levels observed in participants with an evening chronotype compared with those with a morning chronotype. Total PedsQL scores also differed significantly across chronotype groups (p=0.007), with lower scores in the evening chronotype group. Social and school functioning subscale scores were significantly lower in participants with an evening chronotype. HbA1c levels were positively correlated with age and diabetes duration, while total PedsQL scores showed a moderate negative correlation with age. Conclusions: Chronotype was associated with both glycaemic control and quality of life in children and adolescents with type 1 diabetes. Evening chronotype was linked to higher HbA1c levels and poorer psychosocial functioning, particularly in social and school domains. These findings suggest that circadian preferences may be relevant when interpreting metabolic and quality of life outcomes in paediatric type 1 diabetes.