Metastasis to the thyroid gland is very rare. Recently, we experienced a case of thyroid metastasis from breast cancer accompanying a papillary thyroid. A 51-year-old female patient presented with a palpated lymph node on her left lateral neck. The patient had undergone a left modified radical mastectomy followed by chemotherapy and hormonal therapy 12 years prior. Ultrasonography of the neck revealed a malignant looking nodule at the left thyroid lobe, measuring 0.9 × 0.9 cm, and several cystic nodules at the right thyroid lobe. Ultrasonography of the neck additionally revealed a malignant looking lymph node at the right level VI. Fine-needle aspiration of the left thyroid lobe resulted in a diagnosis of papillary thyroid carcinoma and that of the right level VI in Hurthle cell lesion. The patient had a total thyroidectomy with selective dissection of the left neck node. Pathologic assessment of the specimen revealed metastatic carcinoma from the breast carcinoma and papillary thyroid carcinoma. Although the thyroid gland is highly vascularized, metastasis of malignant tumors to the thyroid is relatively rare and detection of metastasis shows a low frequency. So a careful evaluation of thyroid tumor should be considered in a patient with a history of other malignancy.