Primary intracardiac malignant mesotheliomas are extremely rare and carry a very poor prognosis. We present such a case where the lesion encompassed two chambers, the left atrium and ventricle, with no pericardial involvement. Initial echocardiography mimicked a myxoma, and urgent surgical intervention was required in view of significant cardiorespiratory compromise. To the best of our knowledge this is the first case of a primary two-chamber intracardiac malignant sarcomatoid mesothelioma.