Narcolepsy with cataplexy (NC) is associated with hypocretin deficiency, and is thought to be an autoimmunity condition. The mean age at onset is estimated to be in the early 20s. Recent papers have addressed the response to immunotherapies in NC, with challenging results. We report a case of late-onset NC in a patient who did not benefit from early intravenous high-dose immunoglobulin (IVIg) therapy. This is the first reported attempt at using IVIg to treat an NC patient in Korea.