Neonatal severe primary hyperparathyroidism presents in the first days of life with severe life-threatening hypercalcemia. It is associated with an inactivating homozygous mutation of the calcium sensing receptor gene. Total parathyroidectomy is the treatment of choice, so the surgeon must identify all the parathyroid tissue, including supernumerary and ectopic glands. We present the case of an infant who underwent total parathyroidectomy at age 4 months in which intraoperative parathyroid hormone monitoring provided immediate confirmation of surgical cure.