Despite sinus valsalva aneurysm of a well-known pathology, its presence as a cardiac tumor with the RA compression is rare. A 64-year-old man was accidentally identified with a cardiac tumor during the survey of atrial fibrillation. The initial echocardiography and chest computed tomography (CT) displayed a huge mass at right atrium. Surprisingly, the operative findings diagnosed a sinus valsava aneurysm. This case highlights the diagnostic challenges of a huge sinus valsava aneurysm which mimics an intra-cardiac tumor.