Lipomatous atrial hypertrophy (LAH) is a benign cardiac lesion characterized by fat accumulation in the interatrial septum that spares the fossa ovalis. It is associated with obesity and is more frequently observed in elderly and female patients. It is most often detected as an incidental finding on transthoracic echocardiography (TTE). The deposition of adipose tissue may rarely involve both the interatrial septum and the right atrial (RA) free wall. Herein, we describe an extremely rare case of LAH limited to a portion of the RA free wall only, mimicking a myxoma or a thrombotic formation. A multi-instrumental evaluation comprehensive of TTE implemented with pulsed-wave tissue Doppler imaging (PW-TDI), transesophageal echocardiography (TEE), and computed tomography (CT) angiography, performed during the patient's stay in the emergency department, allowed to quickly diagnose the benign RA pseudomass.