Background: Atrial septal defects lead to left to right shunt, the volume of the shunt is determined by RV/LV compliance, defect size, and LA/RA pressure. RV volume overload and pulmonary over circulation are caused by a simple ASD because the RV is more compliant than the LV. The aim of our study was to assess changes in RV systolic function before and after ASD closure either by surgery or transcatheter closure. Methods: This study was conducted on 70 patients diagnosed with ASD Secundum and had subdivided into two groups A (surgical closure) group, and B (percutaneous device closure) group. All patients had been assessed by transthoracic Echocardiography examination for RV systolic Function 24 h before ASD closure, and 6 months after closure. Results: There was a significant decrease in the right ventricle systolic function indices (TAPSE, FAC, Tissue Doppler S wave velocity, and global longitudinal free wall strain) after ASD closure either by surgery or by transcatheter device closure Conclusions: The right ventricle's size and function are affected by a large shunt caused by an ASD secudium. ASD and its consequent volume overload resulted in higher RV myocardial contraction, leading to an increase in strain values and RV systolic function indices, which were reduced and returned to normal values when the left-to-right shunt was eliminated, and the defect was closed.