Background: Coronary slow flow phenomenon (CSPF) is a prevalent clinical syndrome that results in both chronic and acute coronary syndromes (ACS). Early prediction of CSFP in patients with ACS could change the treatment strategy from primary percutaneous coronary intervention (PCI) to pharmaco-invasive strategy with subsequent improvement of patient prognosis. Methods: We performed a cross sectional study in Zagazig university hospitals and Ahmed Maher teaching hospitals in the period between January 2023 and June 2023. We included all patients with ACS and checked for the prevalence of CSFP without obstructive CAD (CAD). Then, we studied the best non0invasive predictors of CSFP in patients with ACS. Results: The study enrolled 100 patients with acute coronary syndrome in the period between January 2023 and June 2023. CSFP without obstructive CAD was detected in 27 (27%) cases. P wave dispersion was the best independent predictor of coronary slow flow (Odds ratio: 1.302 (1.140 – 1.487), P <0.001). The best co-predictors were DM and LA diameter. Conclusions: CSFP is not an uncommon finding among patients with ACS. Among non-invasive predictors, P wave dispersion was the best predictor CSFP in patients with ACS together with DM and LA diameter.