Background: The left ventricular (LV) chamber size and its systolic function is the most common and quickest assessment made by echocardiography, either in the intra operative or intensive care setting, being the pressure generator for the blood supply to the body .Congenital cardiac defects come in two main types: atrial and ventricular septal defects (ASD/VSD). Regression or spontaneous closure may be the natural course of minor septal defects. Aim and Objectives: The aim of the study was to assess the feasibility of speckle tracking echocardiography in estimation of left ventricular systolic function in congenital shunt lesions (ASD, VSD and PDA). Subjects and Methods: This study was done in Tanta University Hospital including 270 patients. The patients were divided into four groups: ASD patients, VSD patients, PDA patients and control subjects. Results: It showed statistically significant difference between ASD, PDA and control group. The difference between the PDA group and the control group was statistically significant. There was a statistically significant difference between the ASD group and the control group in terms of EF percent, FS percent, and ESV ROC curve for Validity of GLS to predict LV systolic dysfunction in PDA Group. Sensitivity was 68 and sensitivity was 80.  Conclusion: It was determined that Speckle-tracking echocardiography offers an additional non-invasive method for evaluating patients' left ventricular function. With congenital shunt lesions.