Abstract Background Acute hyperglycemia is considered an independent prognosticator of both in-hospital and long-term outcomes in patients with acute coronary syndrome (ACS). This study aimed To analyze the incidence of acute hyperglycemia and its impact on the adverse in-hospital outcome in patients with STE-ACS undergoing primary percutaneous coronary intervention (PCI). Methods In this study, we enrolled patients presenting with STE-ACS and undergoing primary PCI at a tertiary care cardiac center. Acute hyperglycemia was defined as random plasma glucose (RBS) > 200 mg/dl at the time of presentation to the emergency room. Results Of the 4470 patients, 78.8% were males, and the mean age was 55.52 ± 11 years. In total, 39.4% (1759) were found to have acute hyperglycemia, and of these, 59% (1037) were already diagnosed with diabetes. Patients with acute hyperglycemia were observed to have a higher incidence of heart failure (8.2% vs. 5.5%; p