As the ethanol stem extracts of Coix lachryma-jobi exhibited hypoglycemic effects in mice, of which the chloroform fractions were the most potent, in this study, the chloroform fractions were tested on streptozocin (STZ) injected mice. The fractions exerted hypoglycemic effects same as the reference drug metformin on hyperglycemic mice induced by both doses of STZ. Meanwhile, the standard drug gliclazide showed hypoglycemic effects only on those mice injected the lower dose of STZ. The hypoglycemic mechanism of Coix lachryma-jobi stems was revealed in part by its effects on insulinemia and hepatic G6Pase activity. In addition, the hypoglycemic effects of the tested fractions were due to gluconeogenetic inhibition, and maybe, improvement of insulin resistance, as well.