Here, we report a case of non-functioning parathyroid carcinoma. A 62-year-old man was referred to our clinic for evaluation of a nodule located posterior to the left thyroid lobe. Ultrasonography revealed a hypoechoic round mass, 12 mm in diameter, which was preoperatively diagnosed as a parathyroid tumor on the basis of the PTH level in the fine-needle aspirate. Under the diagnosis of an intrathyroid non-functioning parathyroid adenoma, the tumor was first excised with the surrounding thyroid parenchyma. After a pathological diagnosis of parathyroid carcinoma was made, left thyroid lobectomy with lymph node dissection was also performed. However, no residual tumor was detected in the specimen. No evidence of disease recurrence has been noted for more than 1 year of follow up.