Abstract Objectives Oxidative stress is closely associated with atherosclerosis and acute coronary syndromes. The purpose of this study was to evaluate well-known and proportional oxidative stress biomarkers in ST-Elevation Myocardial Infarction (STEMI) patients. Methods In this single center, prospective and cross-sectional study, 107 individuals (63 patients) were studied. Total oxidative status (TOS), total antioxidant status (TAS), oxidative stress index (OSI), ischemia modified albumin (IMA), myeloperoxidase (MPO), paraoxonase-1 (PON-1) and arylesterase (AREase) enzyme activities as well as MPO/PON-1, MPO/AREase and MPO/HDL-C ratios were studied. As short-term in-hospital prognosis biomarkers; in-hospital mortality, early systolic dysfunction and spontaneous complete revascularization were investigated. Results Our results indicated that TOS, OSI, IMA, MPO, MPO/PON-1 and MPO/HDL ratios were significantly higher, PON-1 and AREase were significantly lower in STEMI patients compared to the control group. However, in the regression analysis performed by adjusting the differences between the groups, only IMA was found as an independent risk factor (OR=2.711, 95 % CI=1.094–6.719, p=0.031). In terms of in-hospital short-term prognostic biomarkers, a significant relationship was found only between OSI and spontaneous complete revascularization. The OSI value was higher in the group with TIMI grade 3 flow than in the group with TIMI grade 0–2 flow (2.42 [0.81–4.49] vs. 1.63 [0.33–6.07], p=0.016). Conclusions In STEMI patients, both the well-known (TOS, OSI, and MPO) and proportional (MPO/PON-1 and MPO/HDL cholesterol ratios) oxidative stress markers were elevated and can be considered as having a role in the pathogenesis of STEMI.