Idiopathic giant cell myocarditis (IGCM) is a rare disease causing progressive myocarditis characterized by myocardial necrosis and giant cells. Patients often present with rapidly progressive heart failure, ventricular arrhythmias, and heart block. Without treatment, the disease often results in progressive pump failure requiring urgent cardiac transplantation or the need for mechanical circulatory support. The underlying pathophysiologic mechanisms are not yet defined but appear to involve genetics, autoimmune disorders, and possibly environmental factors such as viruses. Combined immunosuppressive regimens appear to prolong survival from death or cardiac transplant. Nevertheless, cardiac transplant is an effective treatment. The disease can recur in the transplanted heart resulting in death or the need for retransplant.