The present work shows the behavior of non-treated and chemical pre-treated peach palm fibers, as reinforcement polymer composites. Chemical treatments with H₂O_2, NaOH, and C₃H₃N and their effects on adhesion performance of the fiber with unsaturated polyester resin are carried out. SEM is used to determine a time exposition of the fibers to chemical reagent and thermal characterization of these fibers after set time is performed. A hand lay-up method is applied to develop the composites and they are tested for tensile strength and Izod impact strength. The TGA of the fibers pre-treated with H₂O₂ 20 V for 144 h show better thermal stability when compared with non-treated fiber. Other treatments do not improve their thermal properties.