Colorectal cancer is the most common synchronous or metachronous cancer in patients with gastric cancer. I report two cases of synchronous and metachronous colon cancer with gastric cancer. Case 1: A 70-year-old man was admitted to our hospital for the treatment of gastric cancer, which had been diagnosed during esophagogastroduodenoscopy (EGD) screening. The recommended preoperative testing was colonofiberscopy (CFS). The CFS revealed a 3-cm ulcerofungating mass, located 20 cm from the anal verge. The pathological report showed a well-differentiated adenocarcinoma. Consequently, we performed radical total gastrectomy and low anterior resection simultaneously. There was no recurrence during the 40-month follow-up of this individual on an out-patient basis. Case 2: A 71-year-old man who was treated with laparoscopically assisted distal gastrectomy (LADG) due to early gastric cancer underwent regular follow-up examination with EGD and abdominopelvic computed tomography. A CFS performed 5 years after the LADG revealed a polypoid mass in the sigmoid colon. The pathological report showed a villous adenoma with adenocarcinoma in situ. The patient underwent a colonofiberscopic mucosectomy. At 36 months after the endoscopic mucosectomy, the patient remained free of recurrence.