An 81-year-old man was admitted with upper abdominal pain and weight loss. Esophagogastroduodenoscopy revealed a large tumor located from the gastric angle to the body. Histological analysis of a biopsy revealed a moderately differentiated adenocarcinoma. Computed tomography revealed metastases in the liver and lung and the patient was subsequently diagnosed with metastatic advanced gastric cancer. He was treated with chemotherapy using S-1 (80 mg/m2) and cisplatin (CDDP) (60 mg/m2). Twenty-two months after chemotherapy, the gastric tumor, and the nodules in the liver and lung, had disappeared. We subsequently diagnosed a clinical complete response. The patient was treated with further S-1 monotherapy for 7 months after complete response assessment. He has lived for more than 7 years since the initial diagnosis without recurrence. Chemotherapy using S-1 and CDDP may be a potent strategy for improving survival in elderly patients with advanced gastric cancer.