BACKGROUND: Sinus of Valsalva aneurysm (SVA) may be congenital or acquired. They could mimic ventricular tumor symptoms and cause signs and symptoms of ventricular outflow tract obstruction. They may also involve the conduction system and cause palpitations or syncopal episodes. Both transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) serve as quick, noninvasive methods to provide information on size and location of aneurysmal dilatation and cardiac chamber involvement. These methods can identify any associated anomalies or complications. This study presents a patient with unruptured SVA. CASE REPORT: A 46-year-old man, who had been suffering from nonspecific symptoms such as exercise intolerance and weakness for a few months, referred to our clinic in Isfahan (Iran). In TTE, a large mass was observed in the right ventricle. SVA was suspected after meticulous probing. This diagnosis was confirmed by TEE and computed tomography angiography. At open heart surgery, an SVA with a lot of clots it was removed. CONCLUSION: SVA must be kept in mind when a tumor-like mass is observed in the right ventricle. Detailed evaluation would thus be necessary to rule out SVA and to prevent wrong diagnosis and treatment that can sometimes be catastrophic. Keywords: Sinus Valsalva, Aneurysm, Cardiac Tumor.