This work reported the study on the effect of alkali treatment using NaOH solutions of different concentration (0-40 wt.%) of sugarcane bagasse fibers on their composition, structure and properties. The results evidenced that treatment modifies the composition, structure and properties of the fibers. The content of hemicellulose and lignin reduce, while cellulose content turns through a maximum as a function of NaOH concentration. A small change in crystallinity was identified and microfibril angle (MFA) remained constant thus structural effects and especially MFA were not the main reasons for altering the properties. The stiffness of the fibers shows a slight maximum at around 2-4 wt.% NaOH content, while a much more pronounced strength found at around 5-8 wt.%. Direct correlation between structure and mechanical properties was not found, indicating that composition is more essential in the determination of properties than structure. The optimum concentration of the treating solution is around 5 wt% NaOH content, if the time of treatment is fixed at 1 hour
