Abstract: Background and Objective: Obesity is one of the main comorbidities impeding cardioprotection in patients with Ischemia Reperfusion (IR) injuries. This study investigated the combined postconditioning effect of melatonin and sitagliptin on myocardial IR-induced arrhythmias in obese rats by evaluating Nitric Oxide metabolites (NOx), oxidative stress and the involvement of the mitochondrial ATP-sensitive potassium channels (mitoK-ATP). Materials and Methods: Sixty-six Sprague-Dawley rats were fed a high-fat diet for 8 weeks to induce obesity. For IR injury modelling, the left coronary artery was ligated for 30 min to induce myocardial ischemia, followed by 2 hrs reperfusion. Melatonin (10 mg kg–1) and sitagliptin (20 mg kg–1) were intraperitoneally administered to obese rats early in reperfusion. Electrocardiography was recorded thoroughly and the Lambeth convention was employed to interpret myocardial arrhythmias (ventricular premature complexes, tachycardia and fibrillation). NOx, oxidative stress markers and mitochondrial function were evaluated using the Griess method, spectrophotometry and fluorometry. Results: Individual application of melatonin or sitagliptin reduced overall arrhythmogenic effects of IR injury in obese rats, however, the effect of their combination was greater on reducing the number, duration, incidence and severity of arrhythmias. The combination of melatonin and sitagliptin also increased the production of NOx, glutathione-peroxidase, superoxide-dismutase and catalase, while reducing malondialdehyde following IR injury. Mitochondrial depolarization and ROS production were also significantly reduced by postconditioning modalities as compared to non-treated IR-experienced obese rats. Interestingly, blockade of mitoK-ATP channels via 5-hydroxydecanoate significantly abolished melatonin/ sitagliptin-induced cardioprotection. Conclusion: Combination of melatonin/sitagliptin conferred considerable anti-arrhythmic influences against myocardial IR injury in obese rats through modulation of mitoK-ATP/NO/ROS signalling.