A case of Wernicke encephalopathy (WE) in the setting of umbilical cord blood transplant is reported. The patient, originally diagnosed with Philadelphia chromosome-positive acute lymphoblastic leukemia, proceeded to an umbilical cord blood transplant. He presented with altered mental status 149 days following transplant. Prompt magnetic resonance imaging, baseline thiamine level, and immediate intravenous replacement allowed for recovery of most symptoms. Accompanying this case is a review of the known cases of WE in hematopoietic cell transplants and their causative factors. This is the first known adult case of WE independent of parenteral nutrition use in the setting of umbilical cord transplant.