We report a case of severe hypothyroidism in a cholangiocarcinoma patient with metastasis to the thyroid gland. A 58-year-old man was admitted for upper abdominal discomfort and multiple palpable neck nodules. Abdominal computed tomography (CT) demonstrated the presence of a 4.7-cm tumor in the right hepatic lobe, and core needle biopsy revealed it to be cholangiocarcinoma. Neck CT showed a diffuse, low attenuation thyroid gland, and fine-needle aspiration (FNA) demonstrated metastatic denocarcinoma. Thyroid function tests were initially normal, but the size of the thyroid gland decreased and severe hypothyroidism developed after chemotherapy was implemented for cholangiocarcinoma. In a patient with malignant disease and a goiter, the possibility of a metastatic tumor involving the thyroid should be seriously considered. Metastatic thyroid cancer and thyroid dysfunction are probably infrequent, but diagnosis is important in the institution of appropriate therapy.