Bisphosphonates (BPs) are often used for the treatment of several diseases such as osteoporosis, cancer-associated hypercalcemia, and osteolytic bone metastasis. Recently, there have been reports of osteonecrosis of the jaw (ONJ) in cancer patients whose treatment regimens include BPs. In this case report, we describe complications and treatment of ONJ in a breast cancer patient with bone metastases who received long-term treatment with BPs. A 70-year-old woman underwent modified radical mastectomy on her left breast cancer and received oral 5-fluorouracil derivatives for 2 years in another hospital. Eleven years after the surgery, she came to our hospital complaining of spinalgia and was diagnosed with recurrent breast cancer with multiple metastases to the stomach, liver, multiple lymph nodes, and spine. After surgery for spine metastases, she was given a combination therapy of trastuzumab (initial bolus: 170 mg/body, followed by two or more cycles of 85 mg/body) every week, docetaxel (100 mg/body) every 3 weeks, and BPs (90 mg/body) every 4 weeks. About 1 year and 4 months later, she complained of pain in her right maxilla; biopsy revealed ONJ. Medical oncologists need to recognize ONJ as a serious side effect of BP treatment; dentists and oral and maxillofacial surgeons need to thoroughly consult patients regarding the administration of BPs and have them make an informed consent.