Abstract Wernicke encephalopathy (WE) is an acute neurological disorder resulting from vitamin B1 deficiency, which is common in chronic alcoholism. We report a rare case of WE due to hyperemesis gravidarum in a 25-year-old pregnant patient at 13 weeks and 5 days of gestation. Initially, the disease manifested as weakness, mental confusion, anterograde amnesia, and visual and auditory hallucinations. The diagnosis was established after the detection of suggestive findings of WE in the thalamus by magnetic resonance imaging (MRI) and a rapid improvement in the patient's clinical status subsequent to treatment with thiamine. Hyperemesis is a rare cause of WE, which makes the reported case important in the literature and reinforces the need for attention in clinical practice to rare but important complications of this common condition (hyperemesis gravidarum).