Wernicke's encephalopathy(WE),characterized by nystagmus and ophthalmoplegia,unsteadiness of stance and gait and mental-status changes,is an acute or subacute metabolic encephalopathy of the central nervous system resulting from Vitamin B1(VitB1)deficiency. A 29-year-old male patient was admitted to our hospital due to abdominal pain and fever. He remained chronically undernourished. He was complicated with WE at the late stage of diagnosis,mainly manifested as the convulsion of limbs,ataxia,and delirium. After treatment with VitB1,these neuropsychiatric symptoms were remarkably resolved. His primary disease was later pathologically confirmed as peritoneal mesothelioma.