 The study investigated the relationship between cellulose crystallinity, extractive content, and physical properties of natural fibers using FTR spectroscopy, x-ray diffraction, and thermogravimetry techniques. Results showed that higher extractive contents associated with lower crystallinity and smaller crystallite size accelerate degradation and reduce thermal stability while increasing cellulose crystallinity and crystallite size shifts thermal decomposition to higher temperatures. This study provides valuable information about the structure and properties of natural fibers for composite formulations before use. This article was authored by Mateus Paletto, ATOR-L, and Atomier J. Zadra.