Background: Obesity is considered to be a pandemic that has increased during the last decades. The energy burning capacity of brown adipose tissue (BAT) makes it an attractive target in anti obesity therapies. Several strategies are being examined to activate and recruit BAT with no side effects. Objective: To use olive tree waste (leaves) as a source of medicinally important phenolic compound oleuropein and to evaluate the possible effects of oleuropein on browning of white adipose tissue in exercised obese Rats.  Material and methods: Sixty adult male Wister albino rats were divided into six equal groups. Group I: Normal control, group II: Oleuropein treated group, group III: High fat diet (HFD), group IV: HFD plus oleuropein, group V: HFD plus exercise training, group VI: HFD plus exercise training and oleuropein. At the end of the experiment, the body weight and the serum levels of lipid profile, GSH, MDA, IL-6 and irisin hormone were determined. The abdominal adipose tissues were excised for the measurement of gene expression of adipose tissue uncoupling protein 1 (UCP1), and CD137. Results: Oleuropein treatment significantly decreased body weight. Serum cholesterol, triglycerides and LDL significantly decreased, while HDL significantly increased. Furthermore, oleuropein suppressed the increase in serum IL-6 significantly. Conclusion: Oleuropein supplementation may provide an effective therapeutic option for combating obesity as it possessed antioxidant and anti-inflammatory activities, as well as increased expression UCP1 and CD137 which promoted additional browning in BAT