We discuss the case of a 5-month-old male British Shorthair referred to our hospital following the detection of a heart murmur during a routine vaccination appointment. Two-dimensional echocardiography revealed a 1.18 mm ventricular septal defect (VSD) located immediately below the aortic valve, without signs of secondary cardiac remodeling. Given the absence of cardiac dysfunction, no treatment was administered, and the cat was periodically monitored over the next 2 years. Echocardiography at 29 months of age revealed no signs of the VSD. Future studies are needed to increase the evidence base for spontaneous VSD closure in small animals.