Hypercalcemic crisis is a severe but rare complication of primary hyperparathyroidism (PHPT), and data on denosumab treatment of patients with this disease is still very limited. The aim of this paper is to investigate the hypocalcemic effect of denosumab in PHPT patients with severe hypercalcemia when surgery should be delayed or is impossible for some reasons. We performed a retrospective study of 10 patients. The analysis included the use of biochemical markers of calcium-phosphorus metabolism, which were followed after the administration of 60 mg of denosumab. The trend to calcium reduction was already determined on the 3rd day after denosumab administration. In most cases the decrease in serum calcium level to the range of 2.8 mmol/L on average or lower was observed on the 7th day ( P = 0.002). In addition to a significant increase in calcium levels we confirmed a significant increase in the estimated glomerular filtration rate on 7th day ( P = 0.012). After that, seven patients underwent successful parathyroidectomy and achieved eucalcemia or hypocalcemia, one patient developed the recurrence of parathyroid cancer after initial surgery, while two patients with severe cardiovascular pathology refused surgery. Our study shows that denosumab is a useful tool in PHPT-associated hypercalcemia before surgery or if surgery is contraindicated.