This study aimed to investigate the diagnostic performance of non-invasive resting myocardial deformation indices in identifying functional significance of intermediate stenosis of the left anterior descending (LAD) artery. Patients with 50–70% LAD stenosis upon coronary angiography were enrolled and divided into group I with fractional flow reserve (FFR) > 0.8 and group II with FFR ≤ 0.8. Patients were subjected to conventional and speckle tracking echocardiography with measurement of myocardial deformation indices including regional peak longitudinal strain (PLS), global longitudinal strain (GLS), Post-systolic strain index (PSI), and time interval between Aortic valve closure (AVC) and PLS. The current study included 200 patients. Group II patients had significantly lower absolute mean values of regional (PLS) and (GLS) compared to group I (− 14.98 ± 5.05 and − 18.73 ± 3.92 vs. − 17.59 ± 3.62 and − 19.20 ± 2.61, p = 0.001 and 0.02, respectively). The FFR values of LAD correlated significantly and negatively with the time interval between AVC and regional PLS (r = − 0.201, p = 0.004) as well as PSI (r = − 0.257, p < 0.001). For identifying cases with FFR ≤ 0.8, the optimal cut-off value of the time interval between AVC and PLS was 76 ms with 77.8% sensitivity and 93.8% specificity. The best cut-off value of PSI was 13%, yielding 50% sensitivity and 87.5% specificity. In patients with intermediate 50–70% LAD coronary artery stenotic lesions, the PSI and the duration between AVC and regional PLS enabled the identification of functionally significant lesions with reasonable diagnostic accuracy.