Tannins are the most abundant resource of natural aromatic polyphenols and an alternative feedstock for the elaboration of chemicals and building blocks to develop value-added polymeric materials. This study is focus on extraction of tannin and modification to obtain green polymeric materials. In this challenge, the extracted tannin was modified from Pinus radiata bark (PBT) by coupling with different aliphatic alkyl carboxylic acid (C2 to C18). Various weight percentage of alkyl chain lengths were introduced into the tannin by esterification or etherification. The resulted modified tannins were characterized by spectroscopic techniques, namely, 1H- and 13C-NMR, and thermal studies by TG analysis and DSC. Spectroscopic studies indicated that the degree of incorporation of alkyl chains depends on the feed of weight % of alkyl chains at modification process. Thermal analyses of the modified tannins reveal that thermal stability was increased for esterified and also etherified tannins compared to the neat tannins. Keynotes: Tannins, extraction, modification, thermal stability, esterification, etherification