A 52-year-old man presented with clinical and echocardiographic signs of cardiac tamponade. A transthoracic echocardiogram revealed a large right atrial mass that obstructed the superior vena cava flow. Cardiac magnetic resonance imaging and computed tomography demonstrated extracardiac tumour invasion of the free atrial wall extending to the right pulmonary hilus. Intracardiac echocardiography-guided biopsy of the tumour revealed the tissue diagnosis-granulocytic sarcoma of the heart. The patient was effectively treated with radiotherapy, chemotherapy and allogeneic haematopoietic stem cell transplantation. He has remained free of the disease for 12 months after treatment.