Congenital Pseudoaneurysm of the mitral aortic intervalvular fibrosa (P-MAIVF) is extremely rare condition. We report a case of neonatal Marfan syndrome with unique and rare diagnosis of case of congenital pseudoaneurysm of the mitral aortic intervalvular fibrosa, where the transthoracic echocardiogram and computed tomography images described a congenital pseudoaneurysm of the mitral aortic intervalvular fibrosa.