A 66-year-old male was diagnosed with advanced gastric cancer with pylorus stenosis, and the first abdominal computed tomography (CT) revealed a large amount of ascites. A staging laparoscopy revealed peritoneal dissemination and positive cytology for numerous amounts of ascites (s-T3(SE), N0, M0, p(+), cy(+), H0, s-Stage IV). The patient received TS-1 orally and paclitaxel administered to the peritoneal cavity. After finishing the second course of the combined chemotherapy, second-look staging laparoscopy was performed, which showed the disappearance of peritoneal dissemination and negative cytology. Chemotherapy combined with oral TS-1 and paclitaxel administered to the peritoneal cavity might be an effective strategy against advanced gastric cancer with peritoneal dissemination.