Abstract Background: The Coronary Slow Flow Phenomenon (CSFP) is defined as a delayed distal vessel contrast opacifi-cation in the absence of obstructive epicardial coronary artery disease during coronary angiography. There is conflicting data in medical literature regarding the effects of CSFP on the left ventricular functions assessed by conventional echocar-diography or tissue Doppler imaging. Aim of Study: To evaluate whether there is impairement of Global Longitudinal Strain (GLS) of the Left Ventricle (LV) obtained by Speckle Tracking Echocardiography (STE) in patients with CSFP and the role of GLS of the left ventricle in prediction of CSFP. Patients and Methods: Patients with chronic stable angina referred for coronary angiography from February 2015 to Augusts 2017 at the Department of Cardiology, Faculty of Medicine; Zagazig University Hospitals were examined. 31 patients with CSFP and 52 age and sex matched controls without CSFP were enrolled in the study. Diagnosis of CSFP was made by TIMI Frame Count (TFC). GLS of LV was measured by two dimensional (2D) STE in addition to other conventional and tissue Doppler parameters to assess LV diastolic and systolic functions. Results: LV GLS was lower in CSFP group patients (–15 ±2.73) compared to control group (–17.19±2.54) (p=0.001). There was statistically significant negative correlation between mean TFC and LV GLS (r=–0.33, p=0.002). LVEF by modified Simpson method was lower in CSFP group (57.77±5.66%) compared to control group (59.29±3.32%) but with no statis-tical significance (p=0.18). Left atrial diameter, LAVI were larger in CSFP group compared to control group (p < 0.05). MV E/Ep and TV E/Ep was higher in CSFP group compared to control group (p < 0.001). Smoking was the only risk factors that showed statistical significance being more common in CSFP patients (p=0.003) with positive correlation between mean TFC and smoking index (r=0.28, p=0.002). Conclusion: CSFP impaires LV systolic and diastolic function, RV diastolic function. We found significant negative correlation between mean TFC and GLS of LV.