Abstract Heparin-induced thrombocytopenia (HIT) is an adverse immune-mediated drug reaction that is associated with thromboembolic complications. We report the case of an 82-year-old man with unstable angina pectoris who suffered from recurrent arterial thromboembolism due to HIT. Coronary angiography (CAG) was performed while we administered unfractionated heparin bolus. CAG showed triple-vessel disease without left main coronary artery. We performed elective percutaneous coronary angioplasty (PCI) to the left anterior descending coronary artery (LAD). The sudden thrombus formation in the LAD occurred during the procedure. We suspected HIT and administered argatroban. We deployed four everolimus-eluting stents in the LAD and intra-aortic balloon pumping (IABP) support was started. The platelet counts were rapidly reduced almost 50% next day after PCI and IgG-specific anti-PF4/heparin antibodies were elevated. Multiple cerebral infarctions were detected by magnetic resonance imaging after the PCI. The patient received the continuous argatroban administration and IABP support for 4 days. Subacute stent thrombosis occurred after quitting argatroban. We performed thrombus aspiration and fibrinolytic treatment. Finally we re-inserted IABP and stabilized the hemodynamic state. Right popliteal arterial thromboembolism occurred after emergency PCI. Argatroban is essential and following oral anticoagulant therapy is necessary to prevent thromboembolic complications. < Learning objective: Heparin-induced thrombocytopenia (HIT) is an adverse immune-mediated drug reaction that is associated with thromboembolic complications. The incidence of HIT in patients who received unfractionated heparin is reported to be 0.1– 1%. We should be aware of HIT when thromboembolic complications occur during the percutaneous coronary intervention procedure. Argatroban is essential and following oral anticoagulant therapy is necessary to prevent thromboembolic complications among patients with HIT.>