Type 2 diabetes mellitus (T2DM) in adolescents represents a clinical challenge related to lifestyle and obesity; however, only a few data are available in developing countries. Therefore, our aim was to investigate the prevalence of T2DM and prediabetes among Brazilian adolescents, as well as to describe the cardio-metabolic profile according to the diagnosis.This is a cross-sectional school-based multicenter study including youth aged 12 to 17 years from cities with more than 100 000 inhabitants in Brazil (n = 37 854 students). Fasting glucose, hemoglobin A1c (HbA1c) and other cardio-metabolic risk factors were measured. Prediabetes was defined by glucose levels 100 to 125 mg/dL or HbA1c 5.7% to 6.4%. T2DM was defined by self-report, glucose ≥126 mg/dL or HbA1c ≥ 6.5%. Multinomial logistic regression was used to estimate the odds ratio (OR) of prediabetes or T2DM according to covariates.Prevalences of prediabetes and T2DM were 22.0% (95% confidence interval [CI] 20.6%-23.4%) and 3.3% (95% CI 2.9%-3.7%), respectively. This estimates represented 213 830 adolescents living with T2DM and 1.46 million adolescents with prediabetes in Brazil. Prevalences of cardio-metabolic risk factors were higher in adolescents with prediabetes and T2DM. In the multinomial logistic model, obesity (OR 1.59, 95% CI 1.20-2.11), high waist circumference (OR 1.51, 95% CI 1.13-2.01), and skipping breakfast (OR 1.48, 95% CI 1.21-1.81) were associated with an increased OR for T2DM, while studying at rural area (OR 0.56, 95% CI 0.41-0.78) was associated with a decreased OR for T2DM.The prevalence of T2DM and prediabetes was high among Brazilian adolescents, which highlights that this disease became a public health challenge not only among adults in Brazil.