Antioxidants are very promising in the combat against diseases. Their ability to sequester free radicals is a potential mechanism in protecting the human cell from further degradation. Gabi (Colocasia esculenta) is a promising natural resource abundant in the Philippines. With this study, characterization of the different functional groups responsible for its antioxidant property was determined. The ethanolic extract of leaf, stalk and tuber were characterized by Fourier Transform Infrared (FTIR) spectroscopy. The antioxidant activity was assessed by the use of 1,1-Diphenyl-2-picrylhydrazyl (DPPH) assay and ascorbic acid content. Results show that various functional groups are present from alcohols, phenols, phenyl ring with mono substitution, alkyl halides, aromatics, amide, heterocyclic amine, alkynes, ester and ether. Statistical analysis showed that phenol content varies significantly among the parts tested (p<0.05). Ascorbic acid content was also shown to vary in content significantly (p<0.05).