 This study evaluates the effect of adding cellulose fiber extracted from sugarcane bagasse on the mechanical properties of fiber-reinforced mortar composites using a 22-factorial design with a central point, and shows that the composites increase flexural strength, with the modulus of elasticity being the most expressive result, due to the good cellulose fiber-cement interface. This article was authored by M. Z. De Pellegrin, J. Accordi, and O. R. K. Montado.