A study of the graft copolymerization of acrylonitrile (AN) onto Chemically modified coir fibers was carried out using a CuSO4 and NaIO4 combination as the initiator in an aqueous medium in a temperature range of 50-70degreesC. The graft yield was influenced by the reaction time, temperature, concentration of CuSO4, concentration of NaIO4, and monomer concentration. Grafting was also carried out in the presence of inorganic salts and organic solvents. A combination of copper(II) and sodium periodate (Cu2+-IO4-) in an aqueous medium with an IO4-concentration of 0.005 mol L-1 and a Cu2+ concentration of 0.004 mol L (1) produced optimum grafting. The chemically modified and AN grafted fibers were characterized by FTIR and scanning electron microscopy (SEM). The SEM studies revealed that grafting not only takes place on the surface of the fibers but also penetrates the fiber matrix. The tensile properties like the maximum stress at break and extension at break of untreated, chemically modified, and AN grafted coir fibers were evaluated and compared. The extent of absorption of water of untreated, chemically modified, and grafted coir fibers was determined. It was found that grafting of AN imparts hydrophobicity onto coir fibers.