We report a case of angiosarcoma arising in the breast following breast-conserving surgery with radiation therapy for breast carcinoma. The patient, a 49-year-old postmenopausal woman, had undergone breast-conserving surgery for invasive ductal carcinoma of the left breast (pT2 pN0 M0 Stage IIA). Adjuvant radiotherapy (50 Gy with a booster dose to the tumor bed of 10 Gy) was then performed for the residual breast tissue and the patient was treated with hormone therapy (tamoxifen, 20 mg daily) for 5 years. She presented with skin erosion with bleeding 10 years after the initial operation. Incisional biopsy revealed angiosarcoma of the breast, and total mastectomy was subsequently performed. The patient was the treated with chemotherapy (weekly paclitaxel, 80 mg/m2 x cycles) and has remained well without evidence of local or distant recurrence.