We herein report a case of severe postsurgical hypocalcemia associated with primary hyperparathyroidism (pHPT), Graves' disease (GD) and acromegaly (AC). A 54-year-old woman was referred to our clinic for treatment of pHPT and GD. She also had active AC and was clinically diagnosed as multiple endocrine neoplasm type 1 because of pHPT and AC. Two enlarged parathyroid glands were detected by preoperative examinations. We performed total parathyroidectomy and thyroidectomy. After the operation, she showed severe hypocalcemia induced by postsurgical hypoparathyroidism and hungry bone syndrome. This is a rare case of postsurgical severe hypocalcemia associated with pHPT, GD and AC.