Heparin-induced thrombocytopenia (HIT) is an immunologically mediated complication of heparin therapy resulting in the consumption of platelets and a catastrophic thromboembolism. Both the clinical and laboratory features are important for a diagnosis of HIT. There have been 3 case reports of suspected HIT in Korea. However none have satisfied the laboratory features. We experienced a case of HIT, which satisfied both clinical and laboratory features, in a patient who received heparin during continuous veno-venous hemodiafiltration (CVVHD) used to treat acute renal failure that developed after a total aortic arch replacement with a cardiopulmonary bypass. The decreased platelet count and obstruction of extracorporeal filter of CVVHD by the blood clot was observed while receiving unfractionated heparin. The serum from the patient contained the anti heparin-platelet factor 4 antibody, and the condition was thus diagnosed as HIT. Argatroban, which is a direct thrombin inhibitor, was used to treat the thrombosis.