Lipomas, which account for approximately 10% of all neoplasms of the heart, may be detected in asymptomatic patients by chance during echocardiography, CT scan, or MRI scan. Occasionally, lipomas are complicated by arrhythmias. We describe a patient who presented with severe cardiomegaly and paroxysmal supraventricular tachycardia. An MRI scan showed a large intrapericardial lipoma with two large cavities inside communicating with each other and with the right ventricular chamber through a defect of the right ventricular wall. The mass was partially removed, and the right ventricle was patched. Surgery combined with antiarrhythmic therapy resulted in a good short-term result.