Background: Atrial septal defect is a common congenital heart anomaly results in hemodynamically significant right ventriclular volume overload and an increase in the pulmonary venous flow. Aim: Evaluate changes of pulmonary venous flow parameters after transcatheter closure of secundum atrial septal defect. Patients and Methods: 50 patients with atrial septal defect aged from 3.5 to 31 years were included in the study. Pulmonary venous flow Doppler and right ventricular function were evaluated before and after successful transcatheter closure by transthoracic and transesophageal echocardiography. Results: The defect size ranged from 15 to 37mm with a mean (24.96 ±7.52), Normal systolic and diastolic waves of pulmonary venous flow Doppler were replaced by a continuous antegrade wave (mean 60±13.6 cm/s) in all atrial septal defect patients. Post-closure, the normal pulmonary venous flow pattern was regained, two separate waves, with a significant decrease in mean peak Systolic wave velocity (44.54±8.12 cm/sec vs 69.61±12.37, P=0.000), the mean peak Diastolic Wave velocity (55.85±9.81 cm/sec vs 72.65±10.38, P=0.000) and a significant increase in the mean peak atrial reversal wave velocity (28.75±4.63cm/sec vs 21.18±3.64, P=0.000). In multivariate regression analysis, significant predictors of haemodynamic significant ASD were ASD size,(odds ratio 1.508, P=0.007, 95% CI 1.153,2.671) and ASD/IAS ratio (odds ratio 2.313, P=0.001, 95% CI 1.064,3.104). Conclusions: Atrial septal defect patients have characteristic pulmonary venous flow pattern: continuous antegrade wave with systolic predominance and decrease in atrial reversal wave, which return to normal after closure. These changes could be helpful echocardiographic tool in prediction of successful closure of the defect.