Importance Mental disorders among children and adolescents are global health concerns. Published studies have provided discordant results regarding treatment rates for mental disorders among youths.Objective To estimate combined treatment rates for several common psychiatric disorders among children and adolescents.Data Sources PubMed, Web of Science, PsycINFO, Scopus, and Embase were searched from database inception until September 23, 2022, and supplemented with hand-searching of reference lists.Study SelectionIncluded studies were those that used validated methods to report treatment rates for any mental disorder, depressive disorders, anxiety disorders, attention-deficit/hyperactivity disorder (ADHD), and behavior disorders among children and adolescents.Data Extraction and Synthesis This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting guideline. Two reviewers independently assessed study eligibility, extracted data, and scored quality. Studies with a Joanna Briggs Institute score of 5 or more were included in the meta-analysis. Treatment rates were pooled using random-effects models. Subgroup analyses were performed to investigate the association with treatment rates of factors, such as year of data collection, World Health Organization region, age, income level, timeframe of diagnosis, informant source, service type, sample origin, and internalizing or externalizing disorder.Main Outcomes and Measures Treatment rates for mental disorders among children and adolescents were the main outcomes, measured as percentage estimates.Results Forty studies were included in the analysis, comprising 310 584 children and adolescents, with boys accounting for 39% of participants (sex was not reported in 10 studies). The pooled treatment rate was 38% (95% CI, 30%-45%) for any mental disorder, 36% (95% CI, 29%-43%) for depressive disorders, 31% (95% CI, 21%-42%) for anxiety disorders, 58% (95% CI, 42%-73%) for ADHD, and 49% (95% CI, 35%-64%) for behavior disorders. Age, income level, and region were significantly associated with the combined treatment rates of mental disorders in children and adolescents. The treatment rate for depressive disorders was higher among adolescents than children (36% [95% CI, 25%-46%] vs 11% [95% CI, 0%-25%]), whereas the treatment rate for anxiety disorders was higher among children than adolescents (64% [95% CI, 52%-75%] vs 20% [95% CI, 9%-30%]). The treatment rate for any mental disorder in lower-middle income countries was 6% (95% CI, 2%-14%), in upper-middle income countries was 24% (95% CI, 2%-47%), and in high-income countries was 43% (95% CI, 35%-52%). For depressive disorders, treatment rates were higher in the Americas (40% [95% CI, 30%-51%]) than in Europe (28% [95% CI, 13%-43%]) and the Western Pacific region (6% [95% CI, 1%-16%]).Conclusions and Relevance This study suggests that, in general, the treatment rates for mental disorders among children and adolescents were low, especially for depression and anxiety. Targeted intervention policies and effective measures should be designed and implemented to improve treatment rates of psychiatric disorders among youths.