 The study aimed to improve the adhesion of ITU and cabuia fibers as reinforcing composites by removing non-cellulosic components through alkali treatment. TAPI standards, FTIR spectroscopy, Polarized Light Microscopy, Gaspecnometry, and SEM were used to investigate the chemical and physical properties of these fibers before and after treatment. The results show that alkali treatment can remove up to 53.9% of lignin and 22.7% of hemicellulose for ITU fiber and 50.7% and 91.7% respectively for cabuia. However, the microfibrella angle is not affected by this treatment. SEM images reveal that ITU fiber has amorphous silica particles on its surface, making it a potential fiber for cement composites. This article was authored by Carlos Tenozoa, Holma Sevastano, Samuel Chaka, and others.