Background Primary percutaneous coronary intervention (PCI) is considered the most preferred strategy in ST-segment elevation myocardial infarction (STEMI). However, the prognostic role of spontaneous re-canalization in STEMI patients is still not clear. The purpose of this study is to evaluate the impact of pre-procedural TIMI flow grade in the culprit coronary artery on the short and long term prognosis in Egyptian patients presented with STEMI and treated with primary PCI. Results A dual center, prospective observational study that was conducted in the period from January 2019 till June 2020 and enrolled 150 STEMI patients presented within 24 h from onset of chest pain. Initial angiography was done with analysis of TIMI flow grade in the infarct related artery. Of the 150 enrolled patients; 93 patients (62%) were found to have initial TIMI flow grade 0 (group A) and 57 patients (38%) had initial TIMI flow grade I–III (group B). There was a strong association between cardiac mortality and pre-procedural TIMI flow grade. 12 mortalities (8% of total study population) were recorded during our study period; in-hospital mortality was reported in 7 patients in group A, yet no mortalities were recorded in-hospital in group B (P value = 0.033). At 1 year follow up; 5 mortalities were recorded in group A with no mortalities at all in group B (P value = 0.005). There was a trend towards an increase in acute heart failure incidence in group A yet no statistically significant value was achieved (P value = 0.112). Target lesion revascularization was reported in 8 patients in group A and in only 3 patients in group B (P value 0.446). Conclusions Despite the evolution in primary PCI strategies and the continuous advancement in anti-thrombotic treatment; pre-interventional infarct related artery TIMI flow grade I–III is associated with better in hospital and 1 year outcome, specifically significantly lower cardiac mortality compared to patients who had TIMI flow grade 0 at initial angiography.