Congenital interventricular septal aneurysms (IVSA) of the muscular septum are rare and can be associated with other familial abnormalities of the ventricular septum, arrhythmias, additional congenital heart disease, and chromosomal abnormalities. IVSA is also linked to ventricular dysfunction and non-compaction, although there are limited reports of this association presenting in utero. We describe a case of fetal ventricular septal aneurysm associated with ventricular dysfunction and pericardial effusion.