Diabetes mellitus was induced in 32 out of 40 adult male albino rats using intravenous injection of 50 mg/kg BW of alloxan. The diabetic rats were divided into four groups, three of which fed a diet containing 8% BW ethanol (polar solvent), cyclohexane (nonpolar solvent) and ether (intermediate solvent) extracts of walnut leaf for 21 days. The-fourth (positive control) group recieved a normal diet. The remaining non diabetic rats (negative control group) recieved neither alloxan nor the above mentioned extracts. Following induction of diabetes mellitus, concentration of serum glucose, cholesterol, triglyceride, blood urea nitrogen, creatinine and the activity of ALT, AST and ALP increased significantly in positive control group compared with negative control group (P<0.05). Compared with the positive control group, the concentration of cholesterol, triglyceride, blood urea nitrogen and creatinine were lower in groups consuming cyclohexane, ether and etanol extracts of walnut leaf (P<0.05). The concentration of glucose and the activity of ALT and ALP in the cyclohexane group were also lower (P<0.05). Comparision between three experimental groups showed that cyclohexane extract ‘of walnut leaf may have more profound effects on levels of serum glucose, blood urea nitrogen, creatinine and the activity of ALT and ALP, than other extracts of walnut leaf. The ethanol extract of walnut leaf had the most effect on cholesterol and triglyceride of diabetic rats.