Cardiac manifestation is the major cause of morbidity in patients with hypereosinophilic syndrome (HES). Clinical features range from heart failure to arterial embolism, which are caused by thickening of the endocardium and mural left ventricular thrombosis. Modern magnetic resonance imaging and echocardiography are able to detect fibrosis, eosinophilic infiltrate and thrombi to stage the fibrotic evolution of the disease. Treatment of HES involves standard medication for heart failure, anticoagulant therapy, immunosuppressive therapy and potentially surgical resection. The outcome of HES depends on both the progression of endocardial fibrosis and associated complications and the 5-year mortality is estimated at 30%.