Components based on composites reinforced with vegetable fibers have awaked interest in various industrial fields. The thermal properties of fibers, matrix and composite define the temperature limits for application and processing of these materials. In this work, a thermal analyzer TGA was used to evaluate the degradation and thermal events of vegetable fibers (abaca, curaua, fique, sisal, cellulose and in natura fibers from sugarcane bagasse and straw), polypropylene (PP) and PP composites reinforced with 15 wt% fibers. Samples were studied by using 30 to 600°C at 5°C.min-1 flow rate under helium or air atmosphere. TG curves from fibers showed weight loss in multiple stages. Before the thermal degradation peak, the abaca composite was more thermally stable, followed by fique, curaua and sisal composites. Thermal stability of composites was inferior for neat PP; however, it had a significant increase for the fiber.