Objectives: In this study, prophylactic effects of natural honey as a pharmacologic preconditioning agent on ischemia/reperfusion (I/R) induced cardiac arrhythmias and Infarct size were investigated in isolated rat heart. Methods: Isolated rat hearts were mounted on a Langendorff apparatus then subjected to 30min regional ischemia followed by 120min reperfusion. In control group, the hearts were perfused by a modified Krebs-Henseleit solution throughout the experiment, however, in the test groups they were perfused by enriched Krebs solution with natural honey (0.25, 0.5 and 1%) 10min before to 10min after ischemia. The arrhythmias were analyzed based on the Lambeth conventions. The Infarct size was determined by Triphenyltetrazolium chloride and planimetry methods. Results: At the ischemia, the total number of ventricular ectopic beats (VEBs) in the control group was 667±116 while perfusion of natural honey (0.25, 0.5 and 1%) reduced it to 128±35 (p<0.01), 161±35 (p<0.01) and 303±94 (p<0.05), respectively. The number of ischemic ventricular tachycardia (VT) and the time spent in VT were significantly lowered by the same concentrations. Honey (0.25 and 0.5%) decreased the incidence of VT from 100% (control) to 13% (p<0.001) and 25% (p<0.01), respectively. During reperfusion phase, the number of VEBs and VT were significantly reduced by all used concentrations. In addition, honey (0.25%) significantly decreased the incidence and time spent for reversible ventricular fibrillation. Moreover, perfusion of honey (0.25, 0.5 and 1%) reduced Infarct size from 46.3±2.9% (control value) to 3.3±1.3, 9.2±1.9 and 11.7±2.2%, respectively (p<0.001 for all). Conclusion: The results of this study showed antiarrhythmic and anti-Infarct properties of natural honey as a preconditioning agent against I/R injuries in isolated rat heart. Probably, antioxidant activity of honey, scavenging of free radicals and presence of energy sources such as glucose may involve in these cardioprotective effects.