Primary leiomyosarcoma of the heart is uncommon and we were able to find only 15 cases reported in the literature. Few of these cases were discovered during life and, as a result, even fewer have been treated surgically. We report a case of a right atrial leiomyosarcoma which was proven pathologically (histologically, immunohistochemically and ultrastructurally) after surgical resection. The clinical presentation, morphological, appearances and outcome are compared with those reported in the literature.