Diabetes is a chronic disease characterized by a disorder in the metabolism of proteins, fats, and carbohydrates. The liver as a non-insulin dependent organ plays an important role in the regulation of blood fat and glucose. Most blood glucose lowering drugs that are introduced for treatment have side effects in long-term consumption. Therefore, to control diabetes and its complications, the use of herbal drugs is widely considered nowadays. The present study investigates the biochemical effects of oleuropein in diabetic male rats. In this study, 30 adult male Wistar rats with a weight range of 190±30 gr were equally divided into 3 groups randomly: 1) control group or intact animals, 2) diabetic animals, and 3) treatment group, which received 60 mg/kg oleuropein for 30 days by gastric gavage. Diabetes was induced in diabetic and treatment groups by injection of streptozotocin (60 mg/kg) intraperitoneally. At the end of the treatment, the levels of triglyceride, cholesterol, LDL, HDL, VLDL, blood glucose, HbA1C, and activity of AST and ALT were determined. The results showed that the serum lipid profile and blood glucose increased significantly in the diabetic group compared with the control group (p<0.05). Also, HbA1C and atherogenic index decreased significantly in the treatment group compared with the diabetic group (p<0.05). This study showed that oral administration of oleuropein has hypoglycemic effects, which can reduce the serum levels of the lipids profile and the atherogenic index in streptozotocin-induced diabetic male rats.