Wernicke's encephalopathy (WE) is a reversible neurological emergency caused by thiamine deficiency. Prolonged vomiting in pregnancy results in thiamine depletion. The early recognition of its clinical signs and symptoms is essential to establish the suspected diagnosis and can be confirmed by MRI. Prompt administration of thiamine is important for preventing the occurrence of sequelae in the mother and for improving the fetal prognostic. We report a case of WE induced by hyperemesis gravidarum with a good maternal and fetal outcome.