In order to improve the mechanical and thermal characteristics of sisal fibers, this study looks at surface modification using alkali and alkali-silane treatments. After being thoroughly washed, sisal fibers were treated with a solution containing 3- aminopropyltriethoxy silane (APTES) and different NaOH concentrations. Significant changes in surface morphology were seen by scanning electron microscopy (SEM) examination after treatment. The alkali-treated fibers (ATF) and alkali-silane-treated fibers (ASTF) showed clear evidence of the elimination of contaminants and fibrillation. Mechanical tests revealed a significant improvement in the treated fibers' tensile strength and Young's modulus, especially at the ideal NaOH concentrations. The treated fibers showed improved thermal stability according to thermogravimetric analysis (TGA), with the ASTF demonstrating the strongest resistance to thermal deterioration. These results demonstrate that sisal fibers may be chemically modified to enhance their mechanical qualities, thermal stability, and surface features, thereby improving their suitability for sophisticated composite applications.