In this study, effect of an ethanolic extract from rhizome of Costus igneus were investigated on activity of following enzyme in liver, kidney, pancreas of streptozotocin (STZ) induced diabetic rats: carbohydrate metabolic enzymes such as glucokinase glucose-6-phosphatase, and fructose-1,6-bisphosphatase in the liver; hepatoproductive enzymes such as aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) in plasma and liver; and antioxidative enzymes such as superoxide dimutase (SOD), catalase (CAT), glutathione peroxidase (GPx), reduced glutathione content (GSH), total sulfhydryl groups (TSH), lipid peroxides (LPO) in liver, kidney and pancreas. An ethanol extract from Costus igneus rhizome was administrated orally at a single dose of 100 or 200 mg/kg per day to diabetes induced rats for 30 days. This study demonstrated that glucose-6-phosphatase fructose-1,6-bisphosphatase, AST, ALT, ALP and LPO levels were significantly increased (p < 0.05), whereas glycolytic enzyme glucokinase, SOD, CAT, GPx, GSH and TSH levels were significantly decreased (p < 0.05) in STZ induced diabetic rats. Oral administration of Costus igneus rhizome ethanol extract [CiREE, 100 or 200 mg/kg per body weight (bw)] and glibenclamide to diabetic rats for 30 days significantly (p < 0.05) reversed levels of these enzymes to normal. Bioactive compound quercetin and diosgenin were isolated from Costus igneus rhizome by high performance thin layer chromatography (HPTLC). These results suggest that, components of CiREE quercetin and diosgenin exhibit antioxidant activity, which was sufficient to reverse oxidative stress in the liver, pancreas and kidney of diabetic rats as well as to stimulate glycolytic enzymes and control gluconeogenesis in diabetic animals.