An 82-year-old man with a secundum atrial septal defect (ASD) underwent transcatheter closure. The patient had a wide area of aortic and superior rim deficiency, with left ventricular diastolic dysfunction and moderate mitral regurgitation. These findings suggested the risk of both cardiac erosion and increased left atrial pressure after closure. To avoid cardiac erosion, a GORE® CARDIOFORM ASD (GCA) occluder (W.L. Gore & Associates, Flagstaff, AZ, USA) was considered an appropriate device in this patient. However, the possibility of excessively high left atrial pressure due to complete defect closure was a concern. Thus, we created a 4.5-mm fenestration using a surgical punch in the fabric membrane of a 44-mm GCA. The device was deployed in an appropriate position, and no significant elevation of pulmonary capillary wedge pressure was observed. One month after the closure, marked improvement in clinical symptoms and continuous flow through the fenestration were observed. This novel fenestration technique may contribute to expansion of the indications for transcatheter ASD closure in patients who require a GCA owing to an anatomically high risk of erosion accompanied by left ventricular diastolic dysfunction. In elderly patients with left ventricular diastolic dysfunction, transcatheter atrial septal defect (ASD) closure is difficult because rapid resolution of an ASD shunt can cause an increase in left atrial pressure. Previous reports described the creation of a fenestration in the closure device. The use of a GORE® CARDIOFORM ASD (GCA) occluder can reduce the erosion risk; however, creating a stable fenestration is difficult. We developed a novel technique to create a stable fenestration in a GCA.