Herein, a rare case of incidentally diagnosed ectopic thymic parathyroid adenoma was described in a 15-year-old girl who had persistent hypercalcemia and elevated PTH for 3 months after the initial presumed curative parathyroidectomy in another center and reoperated in experienced hands with VATS thymectomy, which revealed normalization of PTH and calcium levels early in the postoperative period. Here, PTH is linked to hypercalcemia disease.