Rationale: Prolonged undernutrition may arise out of depression and lead to Wernicke’s encephalopathy if timely diagnosis and intervention are missed. Wernicke’s encephalopathy is potentially treatable, and appropriate treatment may revert clinical depression and cognitive dysfunction to some extent.Patient’s concern: A 69-year-old female who had been taking escitalopram for one year developed tremor, ophthalmoplegia, ataxia, progressive cognitive decline, and convulsions. Diagnosis: Non-alcoholic Wernicke’s encephalopathy and hypomagnesemia due to psychogenic anorexia. Interventions: High dose intravenous thiamine and magnesium were supplemented. Outcomes: The patient showed remarkable improvement in neurological complications and even in depressive features. Lessons: Wernicke’s encephalopathy should not be ignored in the treatment of depression.