An 84-year-old man was admitted to our hospital with new-onset refractory status epilepticus of unclear etiology. On the third day, diffusion-weighted brain MRI demonstrated lesions in the right medial temporal and parietal lobes. As a CSF sample showed pleocytosis, paraneoplastic limbic encephalitis (PLE) associated with small cell lung cancer (SCLC) was suspected. The patient was also positive for anti-gamma aminobutyric acid (GABA)B receptor antibody in the CSF, which has recently been reported in elderly patients with SCLC-related PLE. Methylprednisolone pulse therapy ameliorated the symptoms. It is noteworthy that immune therapy often improves the symptoms of PLE with anti-GABAB receptor antibody, even though radical therapy for the lung cancer may be difficult.