Neuroendocrine carcinoma (NEC) of the colon is a rare and very aggressive tumor with poor prognosis. The current case report presents a 53-year-old male with a 6 cm × 10 cm ascending colon carcinoma, causing large intestine obstruction, with simultaneous multiple hepatic metastases and peritoneal carcinomatosis. Surgical resection of the primary tumor was performed, because of the bowel obstruction, to ameliorate the symptoms before the onset of chemotherapy. Histopathology revealed that the tumor was a small-cell undifferentiated NEC. During the post0operative period, the patient presented pulmonary metastases, and on the 36th post-operative day, death occurred due to respiratory failure.