Abstract Background "ST-segment elevation myocardial infarction (STEMI)" is the most lethal form of "ischemic heart disease (IHD).primary "percutaneous coronary intervention (PCI)" as the first-line treatment for STEMI patients, as it offers better outcomes compared to other medical or surgical options [1,2]. One major concern in interventional cardiology is the occurrence of "slow flow/no-reflow (SF/NR)", which refers to the poor myocardial perfusion to the infarct-related artery as a result of microvascular obstruction. Objectives In this study, we compared the incidence of short-term outcomes between two groups of patients based on the occurrence of intra-procedure "slow flow/no-reflow (SF/NR)" and identified predictors of short-term outcomes. Method This study enrolled a series of consecutive patients who underwent primary "percutaneous coronary intervention (PCI)" for "ST-elevation myocardial infarction (STEMI)". The patients who developed SF/NR during the procedure were compared with their counterparts for the incidence of short-term "major adverse cardiovascular events (MACE)". Furthermore, the study aimed to identify predictors of short-term mortality in these patients. Result In this study, a total of 2,582 patients were included. Among them, 79.1% (2,042) were male. The average age of the patients was 55.7 ± 11.2 years. Intra-procedure SF/NR was observed in 21.7% (560) of the patients. During median short-term follow-up of 180 [144-205] days, patients with SF/NR exhibited higher incidence of all-cause mortality (23.6% vs. 12.3%; p<0.001), and MACE (30.4% vs. 16.9%; p<0.001) with hazard ratio of 1.82 [1.46-2.27; p<0.001] and 1.69 [1.39-2.05; p<0.001], respectively. Among patients with SF/NR, adjusted odds ratio for total ischemic time: 1.04 [1.00-1.07; p=0.041], random blood sugar levels: 1.01 [1.00-1.01; p<0.001], intubation status: 2.79 [1.26-6.18; p=0.011], post-procedure sub-optimal flow: 1.76 [1.04-2.98; p=0.034], and intra-procedural arrhythmias: 5.48 [2.03-14.79; p<0.001] were found to be independent predictors of short-term mortality. Conclusion In conclusion, the presence of intra-procedure SF/NR carries significant prognostic implications. Patients with intra-procedure SF/NR face a significantly higher risk of short-term adverse outcomes.