Background: To evaluate the efficacy of speckle tracking echocardiography (STE) in detecting the existence, degree, and intensity of coronary artery affection in patients with suspected coronary artery disease (CAD). This study aimed to Investigate the ability of STE to identify the existence, size, and intensity of coronary artery affection in individuals with a suspected diagnosis of CAD. Methods: This cross-sectional study enrolled 200 candidates with suspected COD. Patients underwent STE and coronary angiography. Global longitudinal peak systolic strain(GLPSS) was measured and linked with coronary angiography findings for every subject. Results: ROC analysis was done for GLPSS in predicting single-vessel affection. It revealed a significant AUC of 0.713, with confidence interval of 95 percent ranging from 0.555-0.871 (P = 0.013). The best cutoff was ≤- 18, at which specificity and sensitivity were 53.8 and 83 percent. ROC analysis was done for GLPSS in predicting multi-vessel affection. It revealed a significant AUC of 0.908 (P < 0.001). The best cutoff was ≤ - 11, at which specificity and sensitivity were 89.6 percent and 87.7 percent. Conclusion: Two-dimensional speckle tracking echocardiography predicts the existence, size, and degree of CAD with high sensitivity and specificity.