Objective Using data from the Global Burden of Disease Study 2023 (GBD 2023), this study aims to systematically analyze the burden and changing trends of mental disorders among adolescents aged 10-19 years globally and in China from 1990 to 2023, to explore the effects of gender, age, sociodemographic index (SDI), and disease subtype composition, and to predict the incidence trends of adolescent mental disorders up to 2050. Methods Data on the incidence, prevalence, and disability-adjusted life years (DALYs) of mental disorders and their subtypes among adolescents aged 10-19 years globally and in China were extracted from the GBD 2023 database. The trends and differences by age, gender, and were analyzed, and the autoregressive integrated moving average (ARIMA) model was used to predict the incidence of adolescent mental disorders up to 2050. Results From 1990 to 2023, the global prevalence and DALYs of mental disorders in adolescents increased by 31.43% and 39.61%, and by 21.00% and 26.39% in China, respectively. The incidence peaked in 2021 (9 641/100 000 globally and 6 265/100 000 in China). Although it declined thereafter, it remained at a relatively high level. Due to demographic shifts, the absolute number of Chinese adolescents with mental disorders decreased by 10.75% from 1990 to 2023. However, the prevalence and incidence rates showed an upward trend, rising from 14 401.99/100 000 and 4 473.53/100 000 in 1990 to 17 425.46/100 000 and 5 716.24/100 000 in 2023 in China, representing increases of 21.00% and 27.78%, respectively. Moreover, the burden of disease among females aged 15-19 years was much higher than that among males of the same age in China. Globally, anxiety disorders and depressive disorders were the main contributors to the burden of mental disorders, together accounting for more than two-thirds of DALYs. The proportions of anxiety disorders (43.5% in China vs. 42.2% globally) and ADHD (9.0% vs. 4.5%) among all mental disorders were higher in China than the global average. The ARIMA model predicted that by 2050, the incidence of adolescent mental disorders would enter a new high-level plateau with potential risks of fluctuation. The global incidence was predicted to remain at approximately 6 300/100 000 [95% UI: (4 500-8 000)/100 000], and the incidence in China was predicted to be approximately 5 700/100 000 [95% UI: (4 000-7 000)/100 000]. Conclusions Over the past three decades, the burden of mental disorders among adolescents has experienced substantial growth both globally and in China, with China exhibiting a higher increase than the global average. The burdens of anxiety disorders and ADHD are particularly prominent in China, and females in mid-to-late adolescence represent the core population for risk prevention. Notably, although the burden of adolescent mental disorders has declined somewhat after 2021, it remains at a high plateau. There is an urgent need to develop precise prevention and intervention strategies based on gender, age, and disease subtype characteristics in China.