Abstarct: Abstract This study investigates the effects of natural fibers and their decay and weathering on the mechanical behavior of soils. The main objective is to assess the impact of fiber decay and weathering on the compressive strength, strain at failure, and mechanical properties of the soil. The experiments involved mixing fibers with soil at high temperatures (280°C) to simulate decay, conducting unconfined compressive strength (UCS) tests, and performing freeze-thaw cycles to simulate climatic changes. The results showed that as fiber content increased from 0% to 1%, the compressive strength of both wet and dry samples decreased, while the strain at failure increased, indicating greater soil flexibility. In decayed samples, compressive strength and strain at failure decreased by 39.28% and 80.69%, respectively. This reduction was due to increased porosity and the loss of the fibers' reinforcing effect. Cement-stabilized samples with 12% cement exhibited higher compressive strength compared to those with 4% and 8% cement, but their strain at failure was lower due to the cement hydration process and reduced flexibility. Additionally, as curing time increased, compressive strength increased and strain at failure decreased, especially in samples with higher fiber content. In freeze-thaw cycle tests, weight loss increased with higher fiber content, particularly in cured samples. This weight loss was mainly due to voids created by the fibers and the freezing and thawing process, which led to weight reduction and soil compaction. However, these weight changes were minimal and had no significant impact on overall soil stability. This research demonstrates that natural fibers can improve the mechanical properties of soil, but long-term fiber decay reduces compressive strength and strain at failure. Moreover, cement stabilization, particularly at higher percentages, significantly enhances soil strength. The freeze-thaw cycle results also showed that weight and structural changes caused by climate were minimal and had no major impact on soil performance.