Introduction. One of the inflammatory factors affecting the prognosis of myocardial infarction is the high level of neutrophil count in the blood. In this study, we investigated the relationship of neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) in peripheral blood with ST-segment resolution and clinical outcomes of patients with ST-elevation myocardial infarction (STEMI) receiving thrombolytic therapy. Methods. This cross-sectional study was conducted on the patients referring to the emergency department in Tabriz, Iran who were diagnosed with STEMI and began receiving treatment with reteplase. The patients were asked questions to gather information about their demographic characteristics as well as their risk factors, level of response to thrombolytic therapy, etc. For all of the patients, electrocardiogram (ECG) was recorded and different blood tests were performed upon their admission to the emergency department and the obtained data were fed into SPSS Version 19 to explore the possible relationships among different variables. Results. The findings of this study revealed that there is no significant relationship between either NLR or PLR of patients suffering from myocardial infarction and their level of response to thrombolytic therapy. Moreover, no significant relationship was observed between NLR or PLR of these patients and their ejection fraction. However, the results indicated that NLR and PLR associated with an increase in the incidence rate of major adverse cardiac events (MACE) in STEMI patients. Conclusion. The results of this study indicated that NLR and PLR are directly associated with the rate of in-hospital major adverse effects following STEMI irrespective of the ST resolution.