Pseudoaneurysm (dissecting aneurysm) of the membranous septum is a rare occasion. Clinically, aneurysms and pseudoaneurysms not only have the potential to reduce ventricular size, but also can be further complicated by rupture of the aneurysm and by promoting tricuspid insufficiency, aortic valve prolapse, ventricular outflow tract obstruction, and bacterial endocarditis. We describe a case in which a pseudoaneurysm of the membranous septum was identified protruding into the left outflow tract.