 The study aimed to develop polyurethane, PU, composites reinforced with cellulose fibers extracted from sugarcane straw through pretreatment and de-lignefication, using a polyol-to-diosocyanate mass ratio of 1.5 to 1.0, and tested the influence of varying fiber concentrations on thermal, tensile, and moisture absorption properties through chemical characterization and scanning electron microscopy. This article was authored by Patricia Cameramillo, George Jackson DeMauri's Roacher, and Adilson Roberto Goncalves.