Background Atrial fibrillation developing at the acute stage of myocardial infarction is associated with untoward clinical outcomes. The aim of this study was to determine correlations between early statin therapy and atrial fibrillation in acute myocardial infarction.Methods Patients (3396) with sinus rhythm developing acute myocardial infarction were enrolled in the French registry of Acute ST-elevation and non-ST-elevation Myocardial Infarction (FAST-MI). Results Atrial fibrillation developed in 7.0% of patients without and 3.9% of patients with early (≤48 h of admission) statin therapy (p<0.001). Multivariable analysis, including the propensity score for early statin treatment, showed that statin therapy was associated with reduced risk of atrial fibrillation (OR 0.64; 95% CI 0.45 to 0.92, p=0.017). Compared to patients without early statin therapy, the OR for atrial fibrillation were 0.72 (0.49 to 1.04, p=0.080), 0.52 (0.28 to 0.95, p=0.034) and 0.40 (0.18 to 0.92, p=0.030) in patients on conventional, intermediate and high doses respectively. Conclusions This study is the first to document a correlation between early statin therapy and atrial fibrillation at the early stage of acute myocardial infarction.