Tertiary hyperparathyroidism is a state of autonomous PTH secretion that frequently occurs after prolonged periods of secondary hyperparathyroidism. This form of parathyroidism is most frequently seen in patients with kidney failure who undergo successful kidney transplant; however, it can occur in any setting of prolonged secondary hyperparathyroidism. Following kidney transplant, the downstream PTH kidney physiology is re-established, with the negative feedback mechanism ineffective to reduce PTH secretion, leading to an autonomous state. This transition is typically seen in the first few months posttransplant, with the development of hypercalcemia and its associated signs and symptoms. Advanced disease could result in severe hypercalcemia with resultant complications, including calciphylaxis. Treatment typically involves management of underlying residual secondary hyperparathyroidism factors and calcimimetics and, when the glands do not regress, usually requires parathyroidectomy.