This study is aimed at evaluating the biochemical effects and antioxidants activity of extracts of Vernoia calvoana Hook. f (V.C) on STZ induced diabetic rats. Thirty-six (36) rats weighing (100-150g), were divided into 6 groups of 6 animals each. Groups 1 and 2 representing normal and diabetic controls (NC and DC) respectively, receiving placebo, while groups 3-6 represented diabetic treated, receiving 500 mg/kg b.w metformin, 400 mg/kg b.w crude, n-hexane and methanol fractions of V.C, respectively. Treament with drug and extracts of V.C showed a decrease in fasting blod glucose (FBG) in all experimental groups and was significant (p<0.05) on the 7th day of the experimental period, compared to diabetic control. Progressive increase in body weight was observed in all experimental groups compared to DC group. A significant (p<0.05) increase in glutathione peroxidase (GPX) and catalase (CAT) activities were recorded in all experimental treated animal compared to DC and NC. Malondialdehyde (MDA) concentration was observed to decrease significant (p<0.05) in all experimental groups compared to DC. Histopathologically, the changes in pancreatic integrity was consistent with that of biochemical findings. It may be concluded that, extracts of V.C possess potent ameliorative activity against STZ-induced diabetes, via a potential free radical mopping activity.