In the present investigation, am attempt has been made to investigate the in vitro antioxidant potential of aqueous extract of Terminalia belerica bark (TBB). The nitric oxide assay method has been performed at different doses (100-500 mg). The total phenolic contents and total flavonoid contents have also been determined. The results of the present study shows that the aqueous extract of TBB possess antioxidant activity through the DPPH free radical scavenging activity. The preliminary phytochemical investigation indicates the presence of flavonoids and polyphenols. The results are found to be significant when compared with the standard ascorbic acid. Further studies are required to determine the mechanism and isolation of active constituents involved in the antioxidant activity.