In this paper, a case of undifferentiated pleomorphic sarcoma in a patient with right-sided heart failure has been explored. A 61-year-old woman complaining from cough and dyspnea for a week following indistinctive surgery on right buttock area with reported pathology of malignant undifferentiated tumor presented to the hospital. Laboratory results indicated negative TPi enzyme and D.dimer of 4127.81 mg/L. In transthoracic echocardiography, a mass filling the entire right ventricular space was observed. A resection surgery was performed and the pathology was reported as primary cardiac sarcoma.