We report a case of asynchronous bilateral neuroendocrine breast carcinoma. The patient was a 49-year-old woman presenting with a bloody nipple discharge from the right breast. We suspected intraductal papilloma and performed a microdochectomy. A pathological analysis of the resected specimen confirmed the diagnosis as neuroendocrine carcinoma. The tumor was positive for estrogen receptor, progesterone receptor, chromogranin A, and synaptophysin, but negative for the HER2/neu marker. The Ki-67 labeling-index was 40%. As the tumor margin was positive, breast-conserving surgery plus level II axillary lymph node dissection was performed. After surgery, radiotherapy(total dose of 50 Gy)was administered for treating residual breast involvement. Adjuvant hormonal therapy was performed for 5 years. Ten years after surgery, ultrasonography revealed a 12mm irregular hypoechoic mass in the left breast. The mass was diagnosed as a solid tubular carcinoma based on core needle biopsy findings. Subsequently, we performed breast-conserving surgery. The pathological diagnosis was a neuroendocrine carcinoma, and the tumor was positive for estrogen receptor, progesterone receptor, chromogranin A, synaptophysin, and CD56, but negative for the HER2/neu marker. The Ki-67 labeling-index was 50%. We report our experiences with a rare case of asynchronous bilateral neuroendocrine breast carcinoma. In this case, ultrasonography was a useful modality for detecting both the lesions.