Hypereosinophilia-associated syndrome is a rare group of systemic diseases without certain underlying causes. Hypereosinophilic syndrome (HES) and eosinophilic granulomatosis with polyangiitis (EGPA), formerly known as Churg-Strauss syndrome (CSS), are initial considerations, when underlying causes remains unexplained despite of complete evaluation of hypereosinophilia. In this study, we report two rare cases, one case of HES with Loeffler endocarditis, and the other one of EGPA with restrictive cardiomyopathy mimicking myocardial infarction, to further address differential chief cardiac manifestations between HES and EGPA. Key roles of echocardiography played in detection of cardiac involvements, diagnosis, and prognosis prediction are also highlighted.