The objective of the study was to investigate the role of Umbelliferone (UMB) on lipid peroxidation, nonenzymic and enzymic antioxidants in the plasma and liver of streptozotocin (STZ)-induced diabetic rats. Adult male albino rats of Wistar strain, weighing 180-200 g, were induced diabetes by administration of STZ (40 mg/kg b.wt.) intraperitoneally. The normal and diabetic rats were treated with UMB (30 mg/kg b.wt.) dissolved in 10% dimethyl sulfoxide (DMSO) for 45 days. Diabetic rats had an elevation in the levels of lipid peroxidation markers (thiobarbituric acid reactive substances (TBARS), lipid hydroperoxides (HP) and conjugated dienes (CD)), and a reduction in nonenzymic antioxidants (vitamin C and reduced glutathione (GSH) except vitamin E in the plasma and liver, and enzymic antioxidants (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) in the liver. Decreased level of beta-carotene and increased level of ceruloplasmin (Cp) were observed in the plasma of diabetic rats. Treatment with UMB and glibenclamide brought back lipid peroxidation markers, nonenzymic and enzymic antioxidants to near normalcy. Since UMB treatment decreases lipid peroxidation markers and enhances antioxidants' status it can be considered as a potent antioxidant.