The incidence of parathyroid carcinoma is rare. We recently encountered a case of double carcinoma, located in the right and left upper parathyroid glands. A 67-year old man came to the Teikyo University Hospital because of his bilateral parathyroid masses with hypercalcemia and high parathyroid hormone (PTH). Preoperative diagnoses were parathyroid adenoma in the left lobe and papillary thyroid carcinoma or parathyroid carcinoma in the right lobe. First, the left tumor was removed; however, iPTH was still high. The right mass was then resected and iPTH fell to normal range. Histological examination revealed both tumors were parathyroid carcinoma. To the best of our knowledge, this is the first report of double parathyroid carcinoma confirmed histologically.