Factor XI deficiency is rare but may cause life-threatening bleeding during the perioperative period. The clinical manifestation of factor XI deficiency is characterized by bleeding tendency. This unpredictable bleeding tendency makes anesthetic management difficult. We report a case of a partial duodenectomy in a patient with factor XI deficiency. The patient was scheduled for duodenectomy because of a duodenal tumor. When checked for coagulation before surgery, the patient was found to have a remarkably prolonged activated partial thrombin time, and further investigation revealed factor XI deficiency. Fresh frozen plasma was transfused before surgery, and general anesthesia and peripheral nerve block were performed. In the present case of factor XI deficiency, supplementation with clotting factor and proper anesthetic management were important to prevent severe complications.