Diabetes mellitus, a prevalent health issue throughout the world, is characterized by abnormal insulin secretion caused by the overproduction of reactive oxygen species (ROS) which affects the integrity of the lysosomal membrane affecting lysosomal enzymes. It is diagnosed by the presence of hyperglycemia. Natural products as antioxidants can constrict the effect of these ROS. Therefore, treatment of diabetic patients with antioxidant, such as extra virgin olive oil (EVOO) may be of advantage in attenuating certain complications. This study aimed to evaluate the antidiabetic role of olive oil against hyperglycemia in streptozotocin (STZ) induced diabetic rats. Thirty-six healthy male Sprague-Dawley rats were divided into six groups (6 rats per group). Diabetes was induced by single intraperitoneal injection of STZ. Group 1 served as non-diabetic control (NC) and group 2 as diabetic control (DC). Animals in groups 3, 4 and 5 were treated with metformin, olive oil and combination of olive oil with metformin respectively. Rats in group 6 were given olive oil orally for 2 weeks daily before induction of diabetes and then throughout the study. All treatments were gavaged orally for six weeks. The effect of olive oil was assessed by measuring the changes in body weight of rats, determination of glycemic control and estimation of oxidative stress markers. The results showed the significant increase in blood glucose level, glycated haemoglobin (HbA1c) and malondialdehyde (MDA) levels. While as the body weight of rats and insulin were significantly reduced in DC rats. Moreover, MDA level remained higher in diabetic rats treated with metformin and/or olive oil. In contrast, pretreatment with olive oil significantly decreased blood glucose and HbA1c levels. Furthermore, treatment of olive oil with metformin decreased blood glucose and HbA1c levels but it increased total antioxidant capacity (TAC) significantly. In conclusion, pretreatment with olive oil to protect against diabetes and the combined treatment of olive oil with metformin to animals might offer additional antidiabetic and antioxidant effect to metformin. Therefore, it could be a promising strategy for diabetes therapy. We recommend more investigations on humans to study the complementary effect of combination of olive oil and metformin on body tissues.