Aim To identify predictors and construct a model for predicting left ventricular (LV) ejection fraction (EF) in patients with ST-segment elevation myocardial infarction (STEMI). Material and methods This was a prospective registry study of patients with STEMI admitted within the first 24 hours of the disease onset. Patients were evaluated and treated according to the current clinical guidelines. On the first day of STEMI, concentrations of growth stimulating factor, proprotein convertase subtilisin-kex in type 9 (PCSK9), N-terminal pro-B-type natriuretic peptide (NT-proBNP), and high- sensitivity troponin I and C-reactive protein were measured. Echocardiography was performed on the first day and on day 10-12 of admission; LVEF was calculated by the Simpson method. The study included 138 patients; 3 patients were excluded from this part of the study due to death before repeat echocardiography. Based on the LVEF value on day 10-12 of STEMI, the patients were divided into the groups with preserved LVEF (pLVEF) >= 50 % (n=34), reduced LVEF (rLVEF) <= 40 % (n=21), and moderately reduced LVEF (mrLVEF) 41-49 % (n=80). Results The ordinal regression analysis showed that the factors influencing LVEF in STEMI patients included a history of chronic heart failure, Killip class II-IV acute heart failure at the index hospitalization, the development of LV dilation and postinfarction aneurysm, and an increase in NTproBNP. Based on the obtained estimates of the regression parameters, a prognostic model was constructed that showed the highest sensitivity of the model for predicting rLVEF, 94.4 %, mrLVEF, 92.9 %, and a lower sensitivity for predicting pLVEF, 62.5 %. Conclusion In the presence of a history of chronic heart failure, Killip class II-IV acute heart failure, developed LV dilation and postinfarction aneurism, and elevated NTproBNP, patients with STEMI are expected to have lower LVEF values.