Parathyroid carcinoma is exceptionally rare in children. Parathyroid carcinoma in the pediatric population most typically presents with significant hypercalcemia and a palpable neck mass. The authors report the seventh case of parathyroid carcinoma diagnosed in a child younger than 16 years. To our knowledge, this case is the first documented case, in the pediatric population, of parathyroid carcinoma in an ectopically located parathyroid gland with tumor invading the thymus.