Background and Objectives: Apelin is a newly discovered adipokine which plays an important role in regulation of energy homoeostasis and improvement of insulin resistance. However, the effect of exercise training on apelin level in diabetic status is not khown, yet. The aim of this study was to determine the effect of aerobic training on plasma concentration of apelin and insulin resistance in type 2 diabetic rats. Materials and Methods: In this randomized experimental study, twenty diabetic male Wistar rats were divided into training and control group. Diabetes was induced by intraperitoneal injection of nicotinamide and streptozotocin. Four weeks after the development of diabetes, the training group ran 6-week on treadmill. After the training, plasma concentration of glucose, insulin and apelin were measured and HOMA-IR was calculated. Results: There was a statisticaly significant decrease in plasma concentration of glucose and insulin and HOMA-IR, and a significant increase in plasma concentration of apelin was observed in training group compared with control group. Furthermore, a significant negative relationship between plasma concentration of apelin and HOMA-IR after 6 weeks aerobic training was found. Conclusion: It seems that 6-week aerobic training by changes in plasma concentration of apelin, glucose and insulin and HOMA-IR can be effective in treatment of type 2 diabetes in rats.