Aneurysm of sinus of Valsalva is a rare cardiac abnormality. Unruptured aneurysm of sinus of Valsalva is usually asymptomatic and often discovered incidentally. However, a large aneurysm can, in rare cases, cause compression of the ventricular outflow tract. We report a case of 17-year-old male with congestive right heart failure with a large, partially thrombosed unruptured aneurysm of the right sinus of Valsalva. The aneurysmal sac was compressing the right ventricular outflow tract causing marked dilatation of the right ventricle and atrium that was confirmed on contrast-enhanced computed tomography imaging. Unruptured sinus of Valsalva aneurysm causing right heart failure in adolescence has been rarely reported in literature.