INTRODUCTION: Suicide is the 3rd leading cause of death among Brazilian adolescents. Despite the rising rates, national studies on suicide trends still face methodological limitations and data quality issues. This study aimed to investigate adolescent suicide trends in Brazil. METHODS: An ecological time-series study was conducted to analyse suicide (ICD-10: X60-X84, Y87.0) trends among 10-19-year-old adolescents from 2000 to 2022, stratified by sex, age group, and self-harm method. Garbage code redistribution was applied to correct misclassified underlying causes of death. Corrected suicide rates were estimated and time trend analysis was performed using joinpoint regression. RESULTS: After the redistribution, 22,591 adolescent suicides were identified. Rates increased by 120% over the period, with a sharp rise starting in 2013 (APC: 7.7%; 95%CI: 6.2-9.3), particularly among 10-14-year-old girls after 2011 (APC: 10.6%; 95%CI: 8.2-13.0). Male rates were nearly twice as high than female rates, but 10-14-year-old female rates surpassed males after 2018. Hanging was the most frequent method (65.9%), followed by poisoning (15.7%) and firearms (10.8%). Hanging-related deaths increased across all subgroups, and the downward trend in firearm-related suicides reversed after 2010 (APC: 3.0%; 95%CI: 0.6-5.4). CONCLUSIONS: The increasing trend of adolescent suicides in Brazil, notably among young females and through more lethal methods, suggests a deterioration of adolescents' mental health and well-being. The findings underscore the need for comprehensive suicide prevention strategies addressing individual, social, and environmental factors, and the importance of accurate data for policymaking. The study calls for urgent action to tackle the growing problem of adolescent suicides in Brazil.