Strychnos potatorum Linn. is a medium sized deciduous tree belonging to the family Loganiaceae. The collected seeds of Strychnos potatorum were dried and powdered. Methanolic extract of these seeds was prepared by cold maceration. The preliminary phytochemical screening of the crude extract revealed the presence of flavonoids and phenolic compounds. The crude extract was partitioned (gradient) with different solvents like chloroform, ethyl acetate, acetone and water. After conducting preliminary in vitro DPPH free radical scavenging assay on these fractions, the one with maximum antioxidant activity (bioactive fraction) was selected and screened with different in vitro antioxidant methods. The different in vitro antioxidant methods include DPPH free radical scavenging assay, nitric oxide radical scavenging assay, superoxide radical scavenging assay, hydroxyl radical scavenging assay and inhibition of peroxide formation method. The percentage inhibition of free radicals in each method was compared with standard drug. Ascorbic acid and a-tocopherol were used as standard drugs. The seeds of Strychnos potatorum have shown significant antioxidant activity.