Abstract Kleine–Levin syndrome (KLS) is commonly described as a self-limiting disorder exhibiting episodes of hypersomnia and psychiatric symptoms, but without any enduring disabilities. Recently, reports have shown that persistent or even progressive memory deficits can also be associated with the disorder. Nevertheless, little has been reported about cognitive disturbances in KLS. Our report describes a rare patient with KLS and prominent brain atrophy. A 24-year-old woman developed severe neurological and psychiatric features 12 years previously, 2weeks after she was hit in the head. Although she has had no recurrence of the primary KLS symptoms, she continues to have a cognitive disorder, verbal disability, and whole brain atrophy.