A metastatic synovial sarcoma in the right atrium and ventricle is described. A 36-year-old man was admitted to our hospital with generalized fatigue, dyspnoea, and precordial pain. Transthoracic echocardiography demonstrated a metastatic tumour in both the right atrium and right ventricle and revealed obstruction of the inflow tract of the right ventricle caused by a metastatic right atrial tumour. Thoracic computed tomography revealed a pleural-based paravertebral mass in the left intrathoracic cavity and multiple pulmonary nodules in both lungs. Cardiac surgery was performed for palliative treatment due to right cardiac failure and a risk of fatal embolization. The patient died 12 months after the cardiac surgery.