Introduction. Parathyroidectomy is the curative treatment option in primary hyperparathyroidism (PHPT). The decrease of parathormone (PTH) by 50% or more from levels prior to surgery after excision predicts successful parathyroidectomy. Serum calcium is expected to return to normal within 24–72 hours after the surgery; however, nearly 10% have transient, persistent postoperative hypercalcemia. We present a case report of delayed calcium normalization after successful parathyroidectomy in a 38-year-old patient with PHPT. Methods. Parathyroidectomy was performed, with evidence of a decrease in PTH levels of more than 50% in the first 24 hours postoperatively compared to presurgical PTH; however, despite curative parathyroidectomy, a delayed calcium normalization was evidenced, with hypercalcemia persistence up to 120 hours postoperatively. Results. After the first month postoperatively, serum calcium remained normal. In conclusion, approximately 10% of patients with curative parathyroidectomy have transient, persistent postoperative hypercalcemia, which is more likely to occur in patients with higher preoperative serum calcium and PTH levels. Conclusion. Persistent hypercalcemia after the first month postoperatively is related with persistent PHPT, highlighting the importance of calcium monitoring after parathyroidectomy to predict short-term, medium-term, and long-term outcomes and prognosis.