A 45-year-old woman was hospitalized for examination of a cardiac murmur. She had undergone surgery for a membranous ventricular septal defect at the age of 22. Cardiac catheterization showed a membranous ventricular septal aneurysm and a residual shunt. At reoperation, we found the membranous septal aneurysm to be accompanied with a posterior ventricular septal defect. The septal defect was closed with a Dacron patch, and the septal aneurysm was excised, with direct closure. Membranous ventricular septal aneurysm is generally associated with membranous ventricular septal defect. Cases of membranous ventricular septal aneurysm with posterior ventricular septal defect are rare.