Aim: The aim of this study was to evaluate the prevalence and severity of periodontal disease (PD) in adolescents with type 1 diabetes mellitus (DM) and assess the relationship with the clinical and metabolic control of diabetes in adolescents. Material and Methods: A descriptive and analytical study was conducted in patients of both sexes who had a definite diagnosis of type 1 DM and diabetes duration of at least 3 years. An odontologist evaluated PD using the American Dental Association criteria. The measured glycosylated hemoglobin (HbA1c) levels revealed an association between PD and the duration and metabolic control of DM. Results: One hundred and one patients with an average age of 15.02 ± 1.216 years were studied; 59.4% were female. Adolescents with a shorter diabetes duration (3 to 5 years) had a lower prevalence of PD (65.6% versus 34.4%); and for those with a disease duration > 6 years, stages II-IV PD predominated (56.8%, p<0.05). The most severe stages of PD were present in young people with ≥ 9% HbA1c (p<0.001). Males had a higher prevalence of PD than females in terms of disease duration and metabolic control of diabetes (p<0.05). Conclusion: The severity of PD was associated with the duration of diabetes and higher glycemic levels, with worse effects for males than females.