This study was performed to find out the effect of antioxidant enzyme activities of Myrtle extract on endothelial dysfunction in normoglycemic and streptozotocin diabetic (STZ-D) rats. Forty female rats were divided into four groups and were classified as group I (control group), group II (Myrtle treated control group), group III (diabetic group) and group IV (Myrtle treated diabetic group). Plasma glucose, insulin, NO, ADMA, AST, ALT and lipid profile level were measured. Liver and aorta excised and homogenized for the estimation of NO, SOD, catalase and MDA. Our results revealed increased glucose and insulin levels in STZ-D rats as compared to controls but significant decrease in NO in the plasma as well as in the aortic and liver extracts was found. Also our results revealed that Myrtyle improved the increased glucose level. Our study showed increased plasma level of ADMA in STZ diabetic rats compared to controls. Significant increase in the level of MDA in both aortic and liver extracts compared to the other groups. Endogenous antioxidants were significantly reduced and lipid peroxidation significantly increased in STZ-D group. We concluded that Myrtle extract acts as antioxidant and hepatoprotective in diabetic rats