Background: Little is known about the management and mortality rates of ST-segment elevation myocardial infarction patients in developing countries. In this study, to expose independent predictors of early (24 h) in-hospital mortality and ejection fraction, we report our experience with 362 ST-segment elevation myocardial infarction patients admitted to the Istanbul Medical Faculty, Istanbul University, a tertiary referral university hospital, and treated with primary percutaneous intervention. Methods: This is a retrospective study that enrolled all patients (362) admitted with ST-segment elevation myocardial infarction to Department of Cardiology, Istanbul Medical Faculty, Istanbul University, between January 2015 and December 2016. The clinical characteristics of patients were collected retrospectively from medical chart review. Collected data were analyzed using IBM SPSS Statistics (version 21). Results: In the forward stepwise logistic regression analysis, target vessel diameter (p = 0.001), systolic blood pressure (p < 0.001), and troponin T levels (p = 0.007) were independent predictors for early in-hospital mortality, while target vessel diameter (p = 0.03), troponin T level (p < 0.001), heart rate (p = 0.001), and chest pain (p = 0.001) duration were the independent predictors for ejection fraction of 50% and above. Conclusion: Our study is one of the few studies to investigate the predictors of early in-hospital mortality among patients hospitalized with ST-segment elevation myocardial infarction in a tertiary referral university hospital in a developing country. The identified predictors for mortality (including left ventricle ejection fraction and troponin T levels), left ventricle ejection fraction (including troponin T level, chest pain duration), and heart rate are consistent with what has been described in large registries in the United States and Europe.