A 35-year-old man was diagnosed to have gastric cancer by endoscopic and histological examinations. Staging laparoscopy detected peritoneal metastasis. Systemic chemotherapy was started, but the patient complained of severe headache. Subsequently, a lumbar puncture demonstrated adenocarcinoma cells in the spinal fluid, suggesting the occurrence of meningeal carcinomatosis (MC) from gastric cancer. MC occurs only rarely in patients with gastric cancer, but the prognosis is invariably poor. However, this patient nevertheless survived for 12 months after receiving intrathecal MTX/Ara-C together with systemic chemotherapy. Therefore, the early detection of meningeal irritation sign and intrathecal chemotherapy might greatly improve the prognosis of gastric cancer patients with MC.