Aim: Postoperative atrial fibrillation is common after cardiac surgery and is associated with higher rates of complications and mortality. Despite the importance of postoperative atrial fibrillation, the most effective management strategy for this common surgical complication remains uncertain. The aim of this study was to evaluate the effectiveness of amiodarone and early direct current cardioversion to restore sinus rhythm in new onset postoperative atrial fibrillation.Material and Methods: This was a prospective, open-labeled randomized- controlled trial. A total of 50 patients who had new onset postoperative atrial fibrillation longer than 30 minutes were enrolled in the study; 26 patients were randomized to control group and 24 to amiodarone group. Patients in whom sinus rhythm did not return within 24 hours, then external electrical direct current cardioversion was performed for both groups. The primary endpoint of the study was a restoration of sinus rhythm at the 24th hour. Secondary endpoints needed for direct current cardioversion, success rate, sinus rhythm at discharge, sinus rhythm at 30th days and crossover rates.Results: There was a significantly higher number of patients with sinus rhythm at the 24th hour in the amiodarone group than the control group (79.2% vs. 46.2%, p=0.022). Need for direct current cardioversion (p=0.022) and crossover ratio (p=0.021) were significantly higher in control group than amiodarone group. Direct current cardioversion success rate, normal sinus rhythm at discharge and 1st month did not differ significantly between groups. Conclusion: Amiodarone therapy seems effective in restoring sinus rhythm within 24 hours and decreases the need for direct current cardioversion.