We report the case of a 67-year-old woman with non-convulsive status epilepticus (NCSE) due to hyponatremia. She had a history of psychogenic polydipsia but not epilepsy. She was admitted to our hospital with dysbulia. On admission, she was confused and disoriented (Glasgow Coma Scale: 6, E1V1M4). Magnetic resonance imaging of the brain showed no abnormalities. Laboratory test showed hyponatremia (Na+ level: 115 mEq/L). The electroencephalography (EEG) showed a generalized slow wave of 5 Hz during recording. The slow wave was promptly suppressed by diazepam and levetiracetam administered intravenously and orally, respectively. After the hyponatremia was treated the seizures stopped and did not reoccur, even after cessation of the anticonvulsant drugs. The patient was discharged with no neurological deficits. Few reports have described this condition. Here we discuss the diagnosis and treatment of NCSE due to hyponatremia. (Received May 31, 2016; Accepted December 12, 2016; Published April 1, 2017).