Thyroid cancer is an indolent condition that usually presents as a limited disease in the neck. Invasion to vital organs is rarely observed; however, it can be a major cause of mortality, even in well-differentiated thyroid cancers. The common sites of local invasion are strap muscle, recurrent laryngeal nerve, laryngotracheal tree, esophagus, and great vessels in the lateral compartment and mediastinum. Uncontrolled invasion to vital organs in the neck and mediastinum can cause significant morbidity and affect quality of life and survival. Limited involvement of the aerodigestive tract can be controlled by conservative surgical treatments such as shaving-off procedures, while radical resection and subsequent reconstructive procedures are the best choice for more serious cases. In planning the treatment, the risk-benefit ratio should be carefully evaluated to reduce the morbidity, as well as achieve maximal therapeutic effects. Postoperative adjuvant therapies have been the subject of controversy, but there is a general consensus, especially for high-risk patients, that radioiodine therapy and TSH suppression after radical resection are beneficial. The benefits of external beam radiation therapy are unclear, but it should be considered in patients with microscopic residual disease. In conclusion, radical eradication of lesions followed by proper adjuvant therapy is the treatment of choice for locally advanced thyroid cancers.