Childhood cancer survivors (CCS) are at increased risk of developing thyroid disorders during follow-up. Radiation therapy to a field that includes the thyroid gland and 131I-meta-iodobenzylguanidine (131I-MIBG) treatment are the main risk factors for thyroid sequelae, which include decreased thyroid function, hyperthyroidism, thyroid nodules, and differentiated thyroid cancer, specifically papillary thyroid carcinoma. In addition, treatment with anti-neoplastic drugs or immunotherapy may result in thyroid dysfunction. Central hypothyroidism may be seen in CCS after cranial radiotherapy, after immunotherapy, or secondary to a brain tumor that involves the hypothalamic-pituitary region and will be discussed elsewhere in this series. In this chapter, the prevalence, risk factors, surveillance, and management of primary hypothyroidism, hyperthyroidism, thyroid nodules, and differentiated thyroid carcinoma in CCS are discussed.