The aim of this study was to extract cellulose microfibrils from the agricultural residue of coconut palm leaf sheath using chlorination and alkaline extraction process. Chemical characterization of the cellulose microfibrils confirmed that the a-cellulose mass fraction increased from 0.373 kg kg(-1) to 0.896 kg kg(-1) after application of several treatments including dewaxing, chlorite delignification and alkaline extraction of hemicelluloses. Similarly, the crystallinity index obtained from X-ray diffraction for leaf sheath and extracted cellulose microfibrils was found to be 42.3 and 47.7 respectively. The morphology of the cellulose microfibrils was investigated by scanning electron microscopy. The cellulose microfibrils had diameters in the range of 10-15 mu M. Fourier transform infrared and Nuclear magnetic resonance spectroscopy showed that the chemical treatments removed most of the hemicellulose and lignin from the leaf sheath fibers. The thermal stability of the fibers was analyzed using thermogravimetric analysis, which demonstrated that this thermal stability was enhanced noticeably for cellulose microfibrils. This work provides a new approach for more effective utilization of coconut palm leaf sheaths to examine their potential use as pulp and paper and reinforcement fibers in biocomposite applications. (C) 2012 Elsevier Ltd. All rights reserved.