Background: Type 1 diabetes mellitus (T1DM) is one of the most common chronic diseases during childhood and adolescence. It threatens the health and endangers life with consequences for the physical and emotional development of the child and adolescent. Objectives: This study aimed to evaluate the health-related quality of life of adolescents with type 1 diabetes mellitus, associating it with socio-demographic, clinical and biochemical variables. Subjects and methods: A cross sectional study included 124 adolescents with T1DM. Sociodemographic information, metabolic control measures, general and diabetes-related quality of life (QoL), illness profiles, and self-care behaviours were evaluated. Results: Participants' median age was. Males, single, with higher educational level had significantly higher level of quality of life than others. Conclusion: Lower health-related quality of life (HRQoL) was more likely to be experienced by single male adolescents with lower levels of education and high glycated hemoglobin levels.