Enlargement of the bulboventricular foramen (BVF) in double-inlet left ventricle or the ventricular septal defect (VSD) in tricuspid atresia with transposition of the great arteries is one approach for prevention or treatment of systemic ventricular outflow obstruction. Most often, BVF/VSD restriction is bypassed preemptively or addressed directly at the time of Glenn/Fontan procedures as part of staged univentricular palliation. We describe a patient who underwent enlargement of a restrictive VSD during Fontan completion and subsequently presented with an asymptomatic pseudoaneurysm of the right ventricle at the ventriculotomy site.