Benign thyroid teratomas are rare in adolescents and adults. We report on three cases of benign thyroid teratomas that presented as painful tumors in the neck after puberty. The tumor adjacent to the thyroid in each case showed rapid enlargement with predominant cystic lesions within several months. Ultrasonography and computed tomography revealed few findings suggesting the origin of the tumor. Cytological examination and culture of the aspirate failed to show cells originating from the thyroid or infectious findings, but revealed a small population of columnar epithelial cells or squamous epithelial cells. Chemical analysis of the aspirate showed levels of pancreatic enzymes higher than those in serum. The accumulation of cystic fluid in each case was refractory to drainage treatment or percutaneous ethanol injection therapy. The patients subsequently underwent resection of the tumor, and microscopic examination revealed various types of tissue including pancreas, adipose, cartilage, muscle, and skin, and the cystic wall was lined by gastric, intestinal, respiratory, and stratified squamous epithelium. Surgical resection was curative, and subsequent histologic examination revealed mature benign teratomas of the thyroid. The main characteristic of our cases presented the painful tumors due to the enlarged cystic formation lined by a variety of different types of epithelium, which agreed with previous cases of benign thyroid teratomas in adolescents and adults.