Collision tumors of the colon are rare. A 64-year-old man was referred on Emergency County Hospital, Craiova, Romania for the evaluation of intestinal obstruction. Colonoscopy demonstrates the presence of about 9/5 cm sized mass in the rectosigmoid junction. After surgical resection, the rectosigmoid lesion was histopathologically composed of two distinct lesions: mucoid adenocarcinoma in the superficial layer and poorly differentiated neuroendocrin carcinoma in the deeper layer. A rectosigmoid tumor showed two distinct tumors with no admixture or transposition of two neoplastic components. A lymph node metastatic deposit contained both tumors. Immunohistochemical stainings were consistent with mucinous adenocarcinoma and neuroendocrine carcinoma of the two neoplasms. We report this case of colonic collision tumor (mucoid adenocarcinoma and neuroendocrine carcinoma) and review of the literature.