In order to avoid low absorption, incorporation, and undesirable side effects of inorganic oxovanadium compounds, the antidiabetic activities of organic oxovanadium (IV) compounds in alloxan-induced diabetic mice were investigated. Vanadyl carboxymethyl carrageenan (VOCCA) and vanadyl carboxymethyl chitosan (VOCCH) were synthesized and administrated through intragastric administration in different doses for 20 days in alloxan-induced diabetic mice. Glibenclamide was administrated as the positive control. Our results showed that low-dose group, middle-dose group, and high-dose group of VOCCA and VOCCH could significantly reduce the levels of blood glucose (P < 0.05) compared with untreated group, but not in normal mice. Besides, high-dose groups of VOCCA and VOCCH exhibited more significant hypoglycemic activities (P < 0.01). After treated with VOCCH, the oral glucose tolerance of high-dose group of VOCCH was improved compared with model control group (P < 0.05).