Lipomatous Hypertrophy of the Interatrial Septum (LHIS) is an unusual condition usually found as an incidental finding on echocardiography. It can create a mass-like bulge typically sparing the fossa ovalis. We describe a 73-year-old overweight Cypriot woman, who visited our clinic in November 2018 and was complaining of dyspnea on exertion, chest tightness, and two episodes of paroxysmal atrial fibrillation for the last 8 months. A big sessile mass was detected in the interatrial septum measuring 3.7×4.7 cm during transoesophageal echocardiography. The patient underwent resection of the mass and pericardial patch reconstruction of the defect with significant improvement of her clinical status during the follow-up period. The histopathological analysis suggested LHIS. In patients with persistent cardiac symptoms, a prompt resection is a useful option although surgery is generally considered unnecessary in this clinical setting.