Tannins are naturally occurring, high molecular weight polyphenols which can be divided into hydrolysable tannins and condensed tannins. Tannins are the most abundant antioxidants in the human diet and they exhibit many biologically important functions which include protection against oxidative stress and degenerative diseases.The tannin compounds are widely distributed in many species of plants, where they play a role in protection from predation, and perhaps also as pesticides, and in plant growth regulation. The stems, infusion of leaves and roots of Phyllanthusspecies are used in folk medicine for treating intestinal infections, diabetes, the hepatitis B virus and disturbances of the kidney and urinary bladder and it has antioxidants activity. The purpose of the present study was to isolate the tannins from alcoholic extract of P.amarus and to evaluate the in –vitro antioxidant activity of isolated tannins from the extract of dried leaves of P.amarus leaves. Dried leaves of P.amarus were defatted by using Pet.ether 60- 80o C for 48 hours. The extract was used to evaluate the presence /absence of various phytoconstituents. Comparative antioxidant potential of tannins isolated from alcoholic extract of P.amarus was evaluated for the various in-vitro antioxidant activity models. In-vitro anti-lipid peroxidation activity, nitric oxide, superoxide scavenging, DPPH (1,1-diphenyl-2-picrylhydrazyl) scavenging activity were evaluated against standard antioxidants such as Curcumin and ascorbic acid were carried out. Tannins were isolated from Alcoholic extract of P.amarusleaves by lead acetate method and to evaluate its in-vitro antioxidant activity by various models. Isolated tannins from the alcoholic extract of P.amrusshowed significant in-vitro antioxidant activity in all the test systems. The tannins isolated from alcoholic extract of P.amarus showed good in-vitro antioxidant activity for all the antioxidant assays. Tannins isolated from alcoholic extract of P.aramusshowed significant antioxidant activity in all the test systems. Thus the results indicate that the tannins isolated from alcoholic extract of P.amarusare a potential source of natural antioxidants.