The hypoglycemic effects of water and butanolic extracts prepared from leaves of Cecropia obtusifolia (Cecropiaceae) were examined in streptozotocin induced diabetic rats. A single oral administration of a water extract at doses of 90 and 150 mg/kg and of a butanol extract at doses of 9 and 15 mg/kg significantly (P<0.05) lowered the plasma glucose levels in diabetic rats after 3 h administration. Glibenclamide was used as reference and showed similar hypoglycemic effect to the tested extracts at a dose of 3 mg/kg. The flavone, isoorientin and 3-caffeoylquinic acid (chlorogenic acid), were isolated as the important constituents of the plant and were identified as the main constituents in both extracts, too.