Abstract: Well-differentiated liposarcomas are locally aggressive malignant mesenchymal neoplasms, which rarely metastasize to the heart and pericardium. Primary cardiac liposarcomas are extremely rare as well, and in both instances, symptoms are difficult to recognize. Therefore, accurate antemortem diagnosis seldom happens. A rare case of an undiagnosed, primary, well-differentiated cardiac liposarcoma is presented, in a 67-year-old man who suffered a sudden cardiac death. The tumor seemed to arise from the epicardium of the left ventricle and expand into the myocardium of the left ventricle and intraventricular septum. Macroscopic and histopathological findings are presented, as well as a short review of current literature.