The evaluation of the anti-diabetic effects of an organic vanadium(V) complex in streptozotocin (STZ)-induced diabetic rats was investigated. The STZ-induced diabetic rats were orally administrated with sodium 4-amino-2,6-dipicolinatodioxovanadium(V) dihydrate (V5dipic-NH(2)), a vanadium(V) coordination compound. The compound was administered through drinking water at a concentration of 0.1mg/mL for 20 days, and then the concentration was increased to 0.3mg/mL for the following 20 days. At the end of the experiment, V5dipic-NH(2) statistically significantly reduced the levels of blood glucose (P<0.01), serum total cholesterol (P<0.01), triglycerides (P<0.01) and the activities of serum aspartate amino transferase (P<0.05) and alkaline phosphatase (P<0.01) compared to untreated diabetic animals. After treatment with 0.3mg/mL V5dipic-NH(2), the oral glucose tolerance was improved in diabetic animals (P<0.01). In addition, the daily intake of elemental vanadium was markedly decreased in V5dipic-NH(2)-treated diabetic rats compared to vanadyl sulfate (VOSO(4))-treated diabetic rats, which suggested that the anti-diabetic activity of the element vanadium was elevated after being modified with an organic ligand. These results suggested that V5dipic-NH(2), as an organic vanadium compound, is more effective than inorganic vanadium salt at alleviating the symptoms of diabetes.