We present a case of a 66-year-old male with dyspnea and bilateral lower-extremity edema. Pericardiotomy and biopsy were performed and reported malignant mesothelioma. Primary pericardial mesothelioma is a highly malignant tumor that has unfavorable prognosis, and is extremely rare, even among heart tumors. In our case, despite the large amount of pericardial effusion of the first echocardiography, the infiltrated like pericardium was still detected. In addition, cytology after pericardiocentesis reported suspicion of malignancy, which followed by pericardiotomy and biopsy, lead to our timely diagnosis.