An 76-year-old man with right lower abdominal pain underwent abdominal contrast-enhanced computed tomography, which detected a cecal tumor and severe right hydronephrosis.Preoperative total colonoscopy revealed cecal carcinoma and a rectal polyp measuring 25 mm in size for which an endoscopic mucosal resection (EMR) was done. Rectal polyp was diagnosed as a well differenciated adenocarcinoma in adenoma histologically. Early gastric cancer was incidentally found by gastroscopy during a regular physical examination. Considering the patient's age and Alzheimer's dementia, a right hemicolectomy, right nephrectomy and total gastrectomy were done in a two-stage operation. Since the histological examination showed no metastasis of lymph nodes in those aseas, adjuvant chemotherapy has not been used. And no sign of recurrence or metastasis has been seen since the surgery. As synchronous triple gastrointestinal cancers are relatively rare, we report this case and review the literature.