ABSTRACT:The present study was to investigate the antioxidant activity of aqueous bark extract of Spondias pinnata (Linn. f.) Kurz (Family: Anacardiaceae) in streptozotocin-induced diabetic rats. The antioxidant activity was evaluated by the activities of liver enzymes, antioxidant enzymes, and the extent of lipid peroxidation (LPO) in the liver of streptozotocin (STZ) -diabetic rats. S. pinnata extract decreased the LPO by 17%, activities of alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase decreased by 20%, 17% and 36% respectively (P<0.05). The liver reduced glutathione, activities of glutathione reductase, glutathione peroxidase, and glutathione S-transferase of plant extract treated diabetic rats were increased by 43%, 44%, 69% and 52% respectively (P<0.05). The light microscopic appearance of the liver tissue in S. pinnata treated rats has corroborated the biochemical results. The present investigation revealed that the bark extract of S. pinnata exerts significant in-vivo antioxidant activities in diabetic rats.