Vanadyl-meso-tetrakis(4-sulfonatophenyl)porphyrin, VOTPPS, was synthesized and evaluated for its in vitro and in vivo insulin-mimetic activities in streptozotocin (STZ)-induced diabetic mice. Based on the high in vitro insulin-mimetic activity in terms of inhibition of free fatty acid release and enhancement of glucose-uptake in adipocytes, and matallokinetic parameters, VOTPPS was revealed to have a significant hypoglycemic activity in STZ-mice following a single oral gavage of the complex. VOTPPS is thus found to be the first example for orally active vanadyl-porphyrin complex to treat type 1 diabetic animals.