Present work deals with the mercerization of Cannabis indica fibers and their subsequent surface modification by aminopropyl triethoxysilane. The reaction parameters like time and concentration of the sodium hydroxide for mercerization were optimized. C. indica fibers treated with different silane concentration solutions were subjected to evaluation of some of their properties like swelling behavior in different solvents, moisture absorbance under different humidity levels, and resistance toward chemicals such as sodium hydroxide and hydrochloric acid. C. indica fibers treated with 2% aminopropyl triethoxysilane solution have been found more resistant toward moisture, water, and chemicals when compared with that of untreated fibers. Morphological, structural changes, thermal stability, and crystallinity of both silane treated and mercerized fibers have been studied by SEM, FTIR, TGA, and XRD techniques. Silane treatment has been found to cause decrease in crystallinity but increase in the thermal stability of the fibers. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012