Atrial fibrillation (AF) is one of the most common postoperative arrhythmias in patients who undergo coronary artery bypass grafting (CABG). The aim of this study was to evaluate the effect of preoperative atorvastatin on postoperative atrial fibrillation following coronary artery bypass grafting with cardiopulmonary bypass (CCABG). One hundred consecutive patients undergoing elective CCABG, without history of AF or previous statin treatment, were enrolled and randomly assigned to a statin group (atorvastatin 20 mg/d, n = 49) or a control group (placebo, n = 51) starting 7 days preoperatively. The primary endpoint was the occurrence of postoperative AF. C-reactive protein (CRP) levels were assessed in all selected patients before surgery and every 24 hours postoperatively until discharge from hospital. Atorvastatin significantly reduced the incidence of postoperative AF and postoperative peak CRP level versus placebo (18% versus 41%, P = 0.017; 129.3 ± 24.3 mg/L versus 149.3 ± 32.5 mg/L, P < 0.0001). Kaplan-Meier curves confirmed a significantly better postoperative atrial fibrillation-free survival in the statin group (χ² = 7.466, P = 0.006). Logistic regression analysis showed preoperative atorvastatin treatment was an independent factor associated with a significant reduction in postoperative AF (OR = 0.235, P = 0.007), whereas high postoperative CRP levels were associated with increased risk (OR = 2.421, P = 0.015). Preoperative atorvastatin administration may inhibit inflammatory reactions to prevent atrial fibrillation following coronary artery bypass grafting with cardiopulmonary bypass.