Abstract The present study deals with the grafting of barley husk (BH) with lauric acid, palmitic acid and arachidic acid in the presence of redox initiators. The grafting reaction parameters (reaction time, reaction temperature, dimethyl sulphoxide (DMSO) content, fatty acid concentration) were optimized by one variable at a time approach (OVAT) and response surface methodology (RSM) coupled with central composite design (CCD). The crystallinity of BH decreased after grafting of BH with long chain fatty acids. The grafted BH samples showed higher thermal stability as compared to BH and the thermal degradation rate of grafted BH decreased with increase in the chain length of fatty acid. Water contact angle (WCA) of BH was 45° and increased to 140–145° after grafting with lauric acid, palmitic acid and arachidic acid. After grafting, swelling (%) of BH decreased in polar solvents (water, ethanol), however, it increased in dimethyl formaldehyde (DMF). Chemical resistance and hydrophobic transformation of BH improved with an increase in % graft yield as well as with fatty acid chain length.