In the present study methanolic extract of the pulp of plant Brassica oleracea was investigated for the total phenolic content, total flavonoid content and antioxidant activity. Total phenolic content was evaluated by Folin-Ciocalteau method which revealed the presence of very good amount of phenolic content (14.56μg GAE mg-1) in methanol extract. Total flavonoid content was evaluated by aluminium chloride method which revealed the presence of high amount of flavonoid content (22.65μg QE mg-1) in methanol extract. The extract was also analyzed for antioxidant activity by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay and Ferric Reducing Antioxidant Potential (FRAP) assay. In vitro DPPH radical scavenging assay showed potent antioxidant power with IC50 values of 200μl and Ferric reducing antioxidant power for extract (54.16μM/ml) which are comparable to ascorbic acid. The bioactive compounds present in methanolic extracts were characterized by FTIR spectral analysis. The FTIR spectrum showed the presence of alcohols, phenols, alkanes, alkynes, alkyl halides, carboxylic acids and aromatics, aliphatic amines in methanolic extracts. The present study reveals that Brassica oleracea can be used as a potential source of natural antioxidant which may be used to treat various oxidative stress related diseases.