A 37-year-old woman presented with general malaise, anorexia, and nausea. She was hypercalcemic and had an 8-cm- diameter mass in her left breast. Histopathological diagnosis was invasive breast cancer(T3N0M1). She had multiple lung metastases and pleural dissemination, but she did not have bone metastasis. Serum parathyroid hormone-related protein level was elevated. Therefore, it was thought that hypercalcemia was induced by advanced breast cancer. High-volume fluid therapy and bisphosphonate were administered, and electrolyte correction was performed. Her general condition improved after these measures. Although chemotherapy(epirubicin with 5-fluorouracil and cyclophosphamide)was performed twice, breast cancer progressed; therefore, the chemotherapy regimen was changed to nab-paclitaxel, following which the progression of breast cancer was delayed. Left mastectomy was performed to control local tumor enlargement, following which hypercalcemia did not relapse. Hormone therapy showed long-term effectiveness; however, humoral hypercalcemia induced by the malignancy suggested that it was a poor prognosis factor. Aggressive multimodal treatment was important to control tumor growth.