This study examines the chemical and mechanical properties of banana and coconut fibers derived from agricultural waste, with an emphasis on the effects of alkali treatment and epoxy coating. The primary objective is to evaluate the potential of these fibers as sustainable reinforcement materials in geotechnical applications. Fourier Transform Infrared Spectroscopy (FTIR) was employed to characterize the chemical structure of the fibers, while tensile strength tests assessed their mechanical performance. The results indicate that alkali treatment effectively removes lignin and hemicellulose, significantly enhancing the fiber’s tensile strength. Among the varieties tested, Lakatan banana fibers treated with 5% NaOH exhibited the highest tensile strength, while coconut fibers showed optimal performance at 10% NaOH concentration. However, the epoxy coating decreases the breaking force of the fibers by 16%, making it brittle. These findings underscore the potential of agricultural waste as eco-friendly reinforcement materials for soil stabilization applications. Moreover, the study highlights the importance of surface treatments in improving fiber-matrix interactions, which play a crucial role in the mechanical behavior of composite systems.