Longstanding ostium secundum atrial septal defects lead to functional tricuspid regurgitation. Significant functional tricuspid regurgitation associated with left heart valve disease is addressed at the time of primary left heart valve surgery. In contrast, there is no global recommendation for tricuspid regurgitation associated with atrial septal defects. This study assesses changes in tricuspid regurgitation after isolated atrial septal defect closure. Retrospectively, records were examined of 100 patients who underwent isolated ostium secundum atrial septal defect closure without tricuspid valve repair. Echocardiograms were done preoperatively and 3 days, 3 months, and 1 year after surgery. Data on tricuspid regurgitation status, right ventricle dimensions, and pulmonary artery hypertension status were collected and analyzed. After surgical closure, echocardiography showed a regression of tricuspid regurgitation to mild or less in 76% of patients at 3 days, 89% at 3 months, and 93% at 1 year. Severe pulmonary artery hypertension (32% patients preoperatively) showed statistically significant regression: 14% at 3 days, 10% at 3 months, and 2% at 1 year. Preoperatively, the mean right ventricular internal diameter was 37.9 mm, which decreased to 34 ± 5.5 mm (mean ± standard deviation) at 3 days, 32.3 ± 5.3 mm at 3 months, and 31.3 ± 5.4 mm at 1 year. It was also noted that regression favored patients who were <25 years old. Tricuspid valve repair may not be required in patients with ostium secundum atrial septal defect with functional tricuspid regurgitation.