Thyroid cancer is the most common malignancy of the endocrine system, representing approximately 4% of all new cancer cases. The prognosis and treatment of thyroid cancer depend on the tumor type and its stage at the time of diagnosis. An early diagnosis and appropriate treatment plan can improve the prognosis and reduce the possibility of mortality. The standard treatments (surgery and radioiodine treatment) and new options (molecular targeting drugs) for patients with aggressive thyroid cancers have kept the mortality rate of this malignancy low, despite the increase in its incidence. This Special Issue highlights the role of different diagnostic procedures, as well as therapeutic and prognostic markers, in the personalized treatment of thyroid cancer.