Methanol extracts of Commelina communis, a Korean wild edible plant showing hypoglycemic effect on diebetic rats were fractionated systematically by hexane, chloroform, butanol, and water, and these four fractions were administered orally to streptozotocin-induced diabetic rats to evaluate the hypoglycemic effect. The butanol and water fractions of Commelina communis lowered blood glucose levels of diebetic rats at a dose of 500 mg/kg/day. Administration of each fraction except that of chloroform increased the plasma protein levels. Liver protein levels were significantly higher in the butanol- and water fraction-fed groups. The results suggest that the butanol fraction of Commelina communis has hypoglycemic effect on diabetic rats and the intake of Commelina communis may be beneficial for the management of diabetes mellitus.