Background: the complexity of estimating RV geometry and function was well documented and Tricusped Annular Plane Systolic Excursion (TAPSE) is one of the assessment tools of the right ventricle in adults. Aim Of the work: this study aimed to evaluate right ventricular (RV) function in children with atrial septal defect (ASD) and to determine whether TAPSE is an accurate marker of right ventricular (RV) systolic function in patients with atrial septal defect (ASD). Patients and methods: This retrospective study was conducted on 30 Egyptian children with age ranged from 2 months to 18 years of both sexes and they were categorized into two groups, 20 patients group with ASD and 10 control group; they were referred to Cardiology Unit of Al-Azhar University Hospitals in the period from December 2016 to December 2018. The ethics committee of Faculty of Medicine, Al-Azhar University approved this study after verbal and written consents from the parents of these children. All children were subjected to the clinical history, general examination, local examination, chest radiograph, electrocardiogram (ECG) and transthorathic echocardiography examination. Results: there was statistical significant difference in TAPSE results between ASD and non-ASD children, statistical significant difference in ECG finding between ASD and nonASD children, there was a statistical significant positive correlation between TAPSE and right ventricular fractional area changes (RVFAC) in the control group and a statistical significant negative correlation between TAPSE and left ventricle ejection fraction (LVEF). Conclusion: TAPSE is a good indicator for the right ventricular function in children with ASD and a good predictor for development of complications.