An unusual case of advanced synchronous colon and gastric carcinoma is described. A 36 year old female was admitted to our Department with a stenosing right colon cancer diagnosed at endoscopy which was performed for lower crampy abdominal pain and gross blood in the stool. Multiple colon polyps, distal to the tumor, were also detected. On preoperative abdominal computed tomography, a stenosing right colon cancer, without evidence of abdominal diffusion, was confirmed. At laparotomy, in addition to colon cancer, an antral gastric cancer was incidentally found. En bloc hemigastrectomy and subtotal colectomy were performed. Digestive continuity was restored by gastrojejunal and ileosigmoid anastomoses. At histology, a poorly differentiated gastric adenocarcinoma with signet ring-cell component (pT2, pN0; stage IB) and a moderately differentiated colon adenocarcinoma with a tubulovillous component (pT3, pN1; stage III, Stage Dukes C) were revealed. Both tumors showed a low expression of p53 and c-erb2 oncoproteins. No genetic defect was identified in the APC and MMR genes. The patient is alive, without recurrence, two years after the operation.