The study was designed to evaluate the Carica papaya (C. papaya) effect on diabetes mellitus (DM) and its complications. Ninety, clinically healthy white male rats of two months old (100 g average body weight) were divided into equal six groups of 15 rats each. Induction of DM was done by administration of rats by 65 mg/kg body weight (BW) of streptozotocin (STZ). However, C. papaya leaves aqueous extract (0.11 g/mL and 0.22 g/2mL) were administered to rats for 30 days. Our results revealed that after 15 and 30 days post-STZ injection, aqueous leaves extract of C. papaya improved the health status of treated diabetic rats, as serum glucose (276 mg/dL to 186.33 mg/dL), fractosamine (297.44 μmol/L to 272.44 μmol/L), total cholesterol (TC) (139.00 mg/dL to 121.46 mg/dL), triglycerides (TG) (197.69 mg/dL to 179.34 mg/dL), low density lipoprotein-cholesterol (LDL-c) (47.36 mg/dL to 20.90 mg/dL), and L-malondialdehyde (MDA) activity (2.01 nmol/g tissue to 1.81 nmol/g tissue) were decreased, while insulin (1.80 μIU/mL to 2.33 μIU/mL) and high density lipoprotein-cholesterol (HDL-c) levels (52.10 mg/dL to 64.69 mg/dL) and catalase (CAT) activity (66.31 U/g tissue to 71.38 U/g tissue) were increased when compared with untreated diabetic rats. STZ in the recommended dose induced DM and there were changes in previous parameters through reactive oxygen species ROS generation and oxidative stress in β cell of islet Langerhans in pancreas. It could be concluded that C. papaya leaves aqueous extract in doses of 0.11 g/mL and 0.22 g/2mL has antidiabetic, antihyperlipidaemic and antioxidant effect with protective effect on pancreas and other organs. Key words: Clinical pathology, Diabetes Mellitus, Carica papay