Reported is a case of advanced accessory breast cancer to which weekly injection of paclitaxel plus weekly oral administration of cyclophosphamide proved very effective. The patient was a 49-year-old woman who noticed a tumor in the right axilla around October 2007 but then left it alone. In October 2008, the patient visited a nearby physician who made a diagnosis of locally advanced accessory breast cancer. Because the tumor enlarged despite endocrinotherapy, the patient was referred to our hospital in July 2009. CT scan showed a tumor with a size of infant's head, multiple lymph node metastases and metastases to the skin, liver and bones. Following weekly injection of paclitaxel plus weekly oral administration of cyclophosphamide for 4 months, the tumor in the right axilla and metastases to the lymph nodes, skin and liver disappeared. Adverse events were alopecia and grade 1 peripheral neuropathy. The treatment continues at present. Weekly injection of paclitaxel plus weekly oral administration of cyclophosphamide has few adverse reactions and can be performed at an outpatient clinic, suggesting that it is a useful treatment.