Objective Stress hyperglycemia (SH) in a setting of acute myocardial infarction increases the risk of in-hospital mortality. The relationship between SH and in-hospital stent thrombosis (ST) is rare. The aim of our study was to assess the impact of SH on in-hospital ST and prognosis in nondiabetic patients with ST-segment elevation myocardial infarction (STEMI) undergoing a primary percutaneous coronary intervention (p-PCI).Patients and methods This study included 853 patients without diabetes mellitus with STEMI. All patients were treated with p-PCI. Blood glucose (BG) was measured on admission. The patients were divided into two groups on the basis of admission BG (SH, BG180 mg/dl; non-SH, BG<180 mg/dl). The two groups were compared with respect to baseline characteristics and primary endpoints.Results During hospitalization, all-cause mortality was 2.9%. The total incidence of ST was 1.9%. Patients with SH experienced a significantly higher incidence of mortality (P=0.045), ST (P=0.038), and composite major adverse cardiac events (MACE) (P=0.008) than patients without SH. Patients with SH extended hospital days (P<0.001). After multivariate analysis, SH was associated independently with in-hospital mortality, incidence of ST, and composite MACE.Conclusion In nondiabetic patients with STEMI undergoing p-PCI, the patients with SH experienced a significantly higher incidence of mortality, ST, and composite MACE.