We report of a young man who was referred for evaluation of the right atrial mass. He had presented outside the hospital with shortness of breath. A transthoracic echocardiogram (TTE) done there showed a bright echodensity in the right atrium with moderate pericardial effusion. He was treated for presumed viral pericarditis. Pericardiocentesis showed a bloody effusion. Four weeks after this initial presentation, a repeat TTE was done to evaluate for recurrent pericardial effusion due to shortness of breath. The right atrial mass had increased in size and no effusion was noted. He was referred to us for further evaluation. The tumor was successfully resected during surgery, and the pathological examination revealed primary cardiac angiosarcoma. The case highlights the misdiagnosis in initial clinical presentation, current diagnostic modalities, and treatment options for cardiac angiosarcoma.