Leptomeningeal carcinomatosis (LMC) is rare metastatic form of gastric cancer. Most cases are diagnosed in the final stage after multiple distant metastasis. An 84-year-old woman was admitted with melena, headache and vomiting. Esophagogastro-duodenoscopy showed an ulceroinfiltrating lesion at the stomach (Borrmann class III), and biopsy revealed a signet ring cell carcinoma. The abdominal-pelvic CT showed no evidence of metastasis. A sudden decrease of consciousness was noted, but the brain CT showed no active lesion while the brain MRI revealed enhancement of leptomeninges. A lumbar puncture was performed and the cerebrospinal fluid study revealed malignant neoplastic cells. With family consent, no further evaluation and treatment were administered and she died six weeks after the diagnosis of gastric cancer. We report an extremely rare case of a patient who initially presented with neurologic symptoms, and was diagnosed LMC from advanced gastric cancer without any evidence of metastasis in abdomen and pelvis.