Atrial fibrillation (AF) is the most common supraventricular arrhythmia following ST elevation myocardial infarction (STEMI). Oxidative stress and inflammation may cause structural and electrical remodeling in the atria making these critical processes in the pathology of AF. In this study, we aimed to evaluate the association between total oxidative status (TOS), total antioxidative capacity (TAC) and high-sensitivity C-reactive protein (hs-CRP) in the development of AF in patients presenting with STEMI. This prospective cohort study consisted of 346 patients with STEMI. Serum TAC and TOS were assessed by Erel's method. Patients were divided into two groups: those with and those without AF. Predictors of AF were determined by multivariate regression analysis. In the present study, 9.5% of patients developed AF. In the patients with AF, plasma TOS and oxidative stress index (OSI) values were significantly higher and plasma TAC levels were significantly lower compared to those without AF (p=.003, p=.002, p<.0001, respectively). Multivariate regression analysis results showed that, female gender (Odds ratio[OR]=3.07; 95% Confidence Interval[CI]=1.26-7.47; p=.01), left atrial diameter (OR =1.28; 95% CI =1.12-1.47; p<.0001), hs-CRP (OR =1.02; 95% CI =1.00-1.03; p=.001) and OSI (OR =1.10; 95% CI =1.04-1.18; p=.001) were associated with the development of AF in patients presenting with STEMI. The main finding of this study is that oxidative stress and inflammation parameters were associated with the development of AF in patients presenting with STEMI. Other independent predictors of AF were female gender, left atrial diameter and hs-CRP.