Aqueous, ethanolic and chloroform fraction of Syzygium alternifolium leafs were prepared and given different doses of these extracts individually to different batches of rats (both normal and alloxan induced diabetic rats) after an overnight fast. The blood glucose levels were measured at 0, 1, 3, 5 and 7 hours after the treatment. The ethanol extract of Syzygium alternifolium at a dosage of 0.75 g/kg b.w. is showing maximum blood glucose lowering effect in both normal and alloxan induced diabetic rats. The aqueous and chloroform fractions are also showing hypoglycemic and antihyperglycemic activity, but the effect is significantly less than that of ethanol extract. The antihyperglycemic activity of Syzygium alternifolium leafs was compared with the treatment of Glibenclamide.