The antihyperglycemic and hypolipidemic activities of Helicteres isora Linn. (Sterculiaceae) root extracts were investigated in alloxan-induced diabetic rats and a possible mechanism of the blood glucose lowering action was studied. Alloxan-induced diabetic rats experienced 69.13 and 51.14%, 22.60 and 21.89%, 30.12 and 19.96%, and 50.05 and 34.29% reduction in blood glucose, total cholesterol, triglycerides, and urea levels following oral administration of butanol and aqueous ethanol extracts of H. isora root, respectively, at 250 mg/kg for 10 days. The beneficial effects of these extracts were supported by evidence from histological examinations of the liver, pancreas, and kidney. Following the treatment with both extracts, the degenerative changes caused by alloxan in pancreatic cells were restored, particularly with the butanol extract. Histological examination convincingly showed the restoration of pancreatic islets, kidney glomeruli, and liver to its normal size. These results suggest that H. isora roots possess antidiabetic principles and can be useful for treatment of diabetes.