Abstract: The 2025 American Thyroid Association Guidelines for the Management of Differentiated Thyroid Cancer in Adults incorporate the latest evidence-based medical research to systematically update the strategies for diagnosis, treatment, and follow-up of thyroid cancer. Integrating multidisciplinary perspectives from internal medicine, surgery, radiology, pathology, and other fields—and for the first time including input from patient representatives—the guidelines comprehensively cover the entire management process of differentiated thyroid cancer, significantly enhancing their clinical applicability. Regarding the current focus on active surveillance, the new edition provides clear recommendations based on a rigorous evaluation of existing evidence and multidisciplinary input. This article reviews and discusses key updates and practical aspects of the active surveillance section in the guidelines, with reference to relevant Japanese and Korean guidelines, with the aim of improving the application of active surveillance in thyroid cancer management.