Hypocalcemia is one of the common complications after total thyroidectomy. In these patients, the serum parathyroid hormone (PTH), calcium level decreases, and the phosphorus level increases. The level of fibroblast growth factor-23 (FGF-23), a phosphaturic hormone, increases in the serum to normalize the serum phosphorus level. In our study, we aimed to investigate the predictive values of PTH, calcium, phosphorus, 1,25-dihydroxy vitamin D (vitamin D), and FGF-23 tests in revealing patients who will develop hypocalcemia after thyroidectomy. Fifty-seven patients undergoing total thyroidectomy (fifty-two with multinodular goiter, three with Graves’ disease and two with papillary thyroid cancer) were included in this prospective study. Serum PTH, calcium, phosphorus, and vitamin D levels of the patients were measured preoperatively. Ten minutes after complete removal of the thyroid gland, intraoperative PTH (IOPTH) level was measured and the amount of decline in PTH level (PTH decline) was calculated. Postoperative PTH, calcium, phosphorus, vitamin D, and FGF-23 levels were measured 24 h after the operation. Postoperatively, hypocalcemia developed in 7(12.3%) of the 57 patients. IOPTH, postoperative PTH, calcium, and vitamin D levels were significantly lower and PTH decline was significantly higher in patients with postoperative hypocalcemia. Postoperative FGF-23 levels were similar between the groups (p 0.952).