BACKGROUND: Thyroid cancer is a rising concern in children and adolescents, with unique biological behaviors compared to adults. This study aimed to explore the epidemiological trends, pathological features, and regional disparities of thyroid cancer in this population using data from the Global Burden of Disease (GBD) 2021. METHODS: Data on thyroid cancer incidence and mortality from 1990 to 2021 were extracted for individuals under 20 years old. The estimated annual percentage change (EAPC) was calculated to evaluate temporal trends. The Sociodemographic Index (SDI) was applied to assess regional variations. Future trends were projected using a Bayesian age-period-cohort model. RESULTS: From 1990 to 2021, the global incidence of thyroid cancer in children and adolescents increased significantly, with an EAPC of 1.17%. Low-SDI regions exhibited the highest rise in incidence (EAPC: 2.19%), while high-SDI regions experienced a slight decline (EAPC: -0.69%). Mortality decreased globally (EAPC: -0.27%), with notable reductions in high- and middle-SDI regions but stable or increasing rates in low-SDI regions. Females consistently exhibited higher incidence rates across all SDI levels, while males in high-SDI regions showed higher mortality rates. Future projections suggest a steady decline in incidence and mortality rates through 2050. CONCLUSIONS: The increasing incidence and persistent mortality disparities of thyroid cancer in children and adolescents highlight the need for targeted public health interventions. Regions with low socioeconomic development require prioritized strategies to address this growing burden. These findings provide crucial insights for early diagnosis, treatment optimization, and global health policy formulation.