A 55-year-old man with melena was referred to our hospital with suspicion of pancreatic cancer. Upper gastrointestinal endoscopy revealed a type 3 tumor in the greater curvature of the pylorus invading the duodenum. Examination of biopsy specimens showed poorly differentiated adenocarcinoma. Abdominal computed tomography (CT) and positron emission tomography (PET)-CT revealed a gastric tumor in the antrum and regional lymph node metastases invading the pancreas, indicating clinical stage IIIB (cT3, N2, H0, P0, M0) disease. Following 2 courses of neoadjuvant chemotherapy with S-1 plus cisplatin( CDDP), distal gastrectomy with D2 lymphadenectomy was performed. Histological examination revealed no residual cancer cells in the surgically obtained stomach and lymph node specimens, suggesting a complete pathological response( Grade 3). The patient was treated with S-1 for 1 year after surgery. Currently, at 54 months after surgery, the patient is in good health without recurrence.