Thiamine (vitamin B1) is an essential water soluble vitamin that plays an important role in energy metabolism. Thiamine deciency can cause various clinical manifestations ranging from mild neurological and psychiatric symptoms (confusion, reduced memory, and sleep disturbances) to fatal consequences like Wernicke's encephalopathy, ataxia, congestive heart failure, muscle atrophy, and even death primarily in alcoholics. Concurrent illnesses and overlapping signs and symptoms with other disorders can further complicate this. Many patients with sepsis, critical illness develop altered mental states, variously described as disorientation, confusion, delirium and encephalopathy without obvious explanation. We report a case of Wernicke's encephalopathy in sepsis with acute kidney injury in a 26 year old male who is chronic alcoholic without other comorbidities who presented with high grade fever, vomiting for 3 days, difculty in walking and altered sensorium for 1 day. Leucocyte count was elevated on hemogram, renal function tests were abnormal suggesting acute kidney injury, ESR and CRP were raised. MRI ndings were suggestive of Wernicke's encephalopathy and there was signicant improvement in symptoms after thiamine supplementation.