Abstract Napier grass fibers were analyzed by chemical, FTIR and solid-state 13 C NMR methods. These fibers were also treated with 2% and 5% aq. NaOH solutions and the effect of alkali treatment on the composition and structure of the fibers was studied. Alkali treatment eliminated the amorphous hemicellulose component of the fibers to a larger extent. The morphology of the fibers before and after alkali treatment was observed with a scanning electron microscope. The fibers became thin with a rough surface and the cell structure collapsed after alkali treatment and showed enhanced tensile properties.