Incidence of thyroid carcinoma has increased dramatically; however, simultaneous occurrence of different tumors in a single thyroid gland is rare and the embryologic or molecular explanations for such cases lack a solid basis. We report on a 67-year-old woman who underwent surgery for cytologically undetermined nodules in the bilateral thyroid glands. Postoperative pathology findings indicated synchronous occurrence of discrete papillary, follicular, and medullary thyroid carcinoma. She has remained disease-free after postoperative radioactive iodine therapy (130 mCi). This is the fifth report on the synchronous occurrence of different tumors in a single thyroid gland worldwide, and the first ever in Asia.