BACKGROUND Most of the morbidity and mortality from parathyroid cancer is due to PTH-mediated hypercalcemia. Classically, management mainly consists of surgical resection, chemotherapy, and alleviation of hypercalcemia using bisphosphonates and calcium receptor agonists. The use of denosumab in the treatment of parathyroid cancer-mediated hypercalcemia has not been reported. OBJECTIVE The aim of this report is to describe the effect of denosumab on parathyroid cancer-induced hypercalcemia. SUBJECT, MEASURES, AND RESULT: The patient is a 39-year-old man with metastatic parathyroid cancer who presented at age 35. His calcium levels initially responded to surgery, bisphosphonates, calcium receptor agonist, and chemotherapy (dacarbazine). However, his disease progressed, and his hypercalcemia became refractory to these measures in the setting of rising PTH levels. The addition of denosumab, a humanized monoclonal antibody inhibiting receptor activator of nuclear factor κB ligand resulted in successful management of his hypercalcemia for an additional 16 months. CONCLUSIONS Denosumab can be effective in the treatment of refractory hypercalcemia in parathyroid cancer. It may also be of potential use in settings of benign hyperparathyroid-related hypercalcemia such as parathyromatosis, where hypercalcemia is not amenable to surgery or medical therapy with bisphosphonates and calcium receptor agonists.