Cardiac metastasis of Ewing's sarcoma is rare. A 22-year-old woman was admitted with complaints of palpitation and fatigue on exertion. She had a seven-year history of radical right tibial resection for Ewing's sarcoma and was also receiving chemotherapy for lung metastasis of Ewing's sarcoma. Both transthoracic and transesophageal echocardiography demonstrated a single, large (3x3.5 cm) inhomogeneous mass located in the free wall of the right ventricle. To differentiate the mass from a massive thrombus, contrast-enhanced magnetic resonance imaging was performed. The mass showed partial contrast enhancement, suggesting a malignant metastatic mass. Surgical resection was not considered due to accompanying lung metastasis and potentially poor outcome of the operation.