We report a very rare case of occult leptomeningeal carcinomatosis (LC) in whom repeated cytological examination did not show malignant cells in cerebrospinal fluid (CSF) and the primary focus was not discovered by extensive survey. The patient presented with ophthalmoplegia, ataxia and areflexia mimicking Miller Fisher syndrome (MFS) at the initial stage, and later, the clinical profile and laboratory findings including CSF examination simulated tuberculous meningitis. Postmortem autopsy disclosed metastatic signet-ring cell carcinoma infiltrating into cranial nerves and leptomeninges. We would like to emphasize that LC sometimes shows symptoms and signs similar to MFS or tuberculous meningitis.