The present study was planned to confirm the peroxyl radical scavenging capacity of water extract/fractions of Acacia nilotica (L.) Willd. Ex Del. in lipid peroxidation assay and results were compared with standard antioxidant (butylated hydroxytoluene). The bark powder of the plant was extracted with different solvents of increasing and decreasing polarity by maceration extraction method and then the water extract was further partitioned with ethyl acetate and water. The scavenging activity of extract was found to increased on fractionating the extract.