<p>Soil desiccation can cause erosion of embankments, leaving them ineffective in resisting flood water, which leads to recurring misery for the people dwelling in flood-prone regions. The tensile strength developed due to fiber inclusion, when combined with the cementation induced by a chemical additive, can effectively reduce the cracking tendency of soil. While polyester fiber is readily available and economical, utilizing fly ash provides a sustainable and economical means to handle this problematic industrial byproduct. As such, this study evaluated the effectiveness of varied proportions of polyester fiber and fly ash in reducing desiccation cracking by mixing them with embankment soil collected from Sunamganj, a flood-prone region in northeastern Bangladesh. Crack area and volume were estimated from the binary images and three-dimensional soil models, which were generated using image processing software. Moreover, the influence of the optimum fiber and fly ash contents on various soil properties was investigated by conducting laboratory tests such as Atterberg limits, compaction, expansion index, free swell index, and unconfined compressive strength tests, whereas their effects on the soil microstructure were evaluated by performing scanning electron microscopy analysis. The study’s findings revealed that with the increase in fiber and fly ash content, crack width and depth reduce, consequently minimizing crack area and volume. Adding 1.5% polyester fiber and 15% fly ash to the soil decreased the surface cracking by 96.36% and crack volume by 97.84%. Scanning electron microscopy results provided evidence of adhesion between soil and fiber as well as the clustering effect of fly ash, which plays a significant role in restricting soil cracking. The use of the additives also led to a notable improvement in soil properties. Soil plasticity, free swell index, and expansion index were reduced by 33.58%, 47.32%, and 60%, respectively, while the compressive strength of soil was increased by 45%.</p>