Apelin is an adipocyte-derived peptide that plays an important role in regulation of energy homoeostasis and decrease of insulin resistance. We investigated the effects of exercise training on adipose tissue apelin expression in streptozotocin-nicotinamide induced diabetic rats. In this experimental study, 38 male Wistar rats were assigned to 4 groups: sedentary non-diabetic, trained non-diabetic, sedentary diabetic and trained diabetic. Type 2 diabetes mellitus (T2DM) was induced by intraperitoneal injection of streptozotocin and nicotinamide in adult rats. The trained groups ran 8-week on treadmill progressively for 45 min at a speed of 24 m/min and a 5% grade. After the training period, an intraperitoneal glucose tolerance test was performed in addition to the measurement of blood lipids and plasma apelin levels. Apelin mRNA levels in visceral adipose tissue were also analyzed. Two-way repeated measures analysis of variance (ANOVA) and Pearson correlation coefficient was used for analyzing data. P < 0.05 was considered to be statistically significant. Results indicated a significant decrease of insulin resistance followed by a significant increase of plasma levels and mRNA expression of apelin in trained diabetic compared with sedentary diabetic rats. Furthermore, apelin levels did not correlate significantly with body weight and epididymal fat weight in trained diabetic rats. In conclusion, the findings revealed that chronic exercise training, independently of body weight and fat pad weight by decrease of insulin resistance can increase apelin levels in visceral adipose tissue, thereby attenuating the progression of diabetes and decreasing insulin resistance in T2DM rats.