This study was aimed to investigate the possible protective effects of different amount of olive leaf extracts and infusion on some biochemical and haematological parameters of streptozocin-induced experimental diabetic rats. For this purpose, 56 Wistar albino rats were randomly divided into 7 groups (n=8). Biochemical and haematological analyses were performed at the end of the 21-day trial. It was observed that HGB, HCT, MCV were positively affected (p<0,05), while RBCs were not statistically significant affected in all OLE-applied groups. In diabetes+OLE-50 and OLE-100 groups, WBCs significantly decreased compared to the that of control group (p<0,05), while statistically significant change was not observed in the OLE-25 group. The cholesterol values of the diabetes+OLE-25 group were significantly lower than those of the control group (p<0,05), while the increase in the diabetes+OLE-100 group was significant at the statistical level (p<0,05). The increase in diabetes+OLE-50 group was not significant. In the diabetes+OLE-25, diabetes+OLE-50 and diabetes+OLE-100 groups, triglyceride decreased significantly (p <0,05) in comparison to diabetic group. In the infused diabetic group, RBC, HGB, HCT, MCV, MPV, PDW and EOS were significantly increased in the positive direction (p <0,05). Infusion was found to have negative effect on triglyceride; LDL, Cl, Na. HDL, Mg and P were found to be affected positively. It was determined that the most effective dose on cholesterol and triglycerides in OLE-administered groups is OLE-25 mg/kg. Infusion was found to have positive effect on HDL, while LDL was affected negatively. On the other hand, the decrease in cholesterol was found to be not statistically significant, while the decrease in triglyceride was significant.