Thyroid cancer is one of the malignant tumors with an increasing incidence worldwide, in which, papillary thyroid carcinoma (PTC) and medullary thyroid carcinoma (MTC) occasionally exhibit superior mediastinal lymph node metastasis (SMLNM). Although this is still considered regional metastasis, it is indicative of a later stage of the disease and is prone to being misdiagnosed or undertreated. For common types of PTC and MTC, thorough dissection of the central compartment, lateral neck, and the rare superior mediastinal lymph node metastases (SMLNM) can significantly improve disease-free survival rates. Anatomically, the thyroid has an extensive lymphatic drainage network. The intrathyroidal lymphatic network connects both lobes of the gland through the isthmus, while the extrathyroidal lymphatics drain to the mediastinal lymph nodes. Currently, there is no specialized and mature classification for SMLNM in thyroid cancer, hence the classification of lung cancer is commonly used. The most common regions for thyroid cancer SMLNM are zones 2R and 2L, with zones 4R and 3a being relatively less common. The incidence of SMLNM ranges from 0.7% to 48.1%. The mediastinal lymph node metastasis rate for PTC is approximately 6% to 12%, while MTC, which more readily metastasizes to lymph nodes, has a metastasis rate of up to 18%. Clinically, SMLNM often presents without obvious symptoms and is commonly detected through imaging examinations or tumor marker tests. Ultrasound examination has difficulty detecting SMLNM. Typical features on enhanced neck and chest CT scans include enhancement, calcification, cystic changes, and invasion. Enhanced MRI, PET, and ¹³¹I scans can also assist in the diagnosis. For thyroid cancer patients with SMLNM, safe, standardized, and thorough surgery remains key to achieving good outcomes, with individualized surgical plans tailored to the specific circumstances of each patient. Surgical principles include aiming for R₀ resection in a single session whenever possible, ensuring complete dissection while maintaining surgical safety to achieve both anatomical and biochemical cures. Surgical approaches may include open neck surgery, sternotomy, endoscopic-assisted surgery, and thoracoscopic surgery. Most dissections can be completed through the cervical approach; however, extensive low-level metastasis or severe invasion of surrounding major blood vessels may require sternotomy, sometimes with endoscopic assistance and/or thoracoscopic surgery. Postoperative care should focus on avoiding complications such as major vessel tears and injuries to the trachea and esophagus. Given the complex anatomical structure of the superior mediastinum, its difficult exposure from the neck, and the high surgical risk, thyroid or head and neck surgeons often face relative unfamiliarity and challenges, necessitating multidisciplinary collaboration. Although patients with thyroid cancer metastasis to the superior mediastinum generally have a poorer prognosis, the use of individualized surgical approaches and plans, in conjunction with thoracic and cardiovascular surgeons, for complete dissection of mediastinal metastases can significantly improve patient prognosis and quality of life. This article reviews the surgical diagnosis and treatment of thyroid cancer SMLNM to provide a reference for thyroid surgeons in their clinical practice.