Expansive soils, characterized by significant volume changes in response to moisture fluctuations, present substantial engineering challenges globally. This study explores the efficacy of lignosulfonate (LS), an industrial by-product, as a sustainable stabilizer for expansive soils. Three soil samples with varying degrees of expansiveness (weak, mid, and strong) were treated with LS, and their geotechnical properties were evaluated. For weak, mid, and strong expansive soil, the optimum lignosulphonate content (OLS) determined based on the free swelling rate and plasticity index was 0.75%, 2%, and 6%, respectively. The addition of LS resulted in a reduction of the liquid limit, plasticity index, and free swell index across all soil types. Furthermore, LS-treated soils exhibited enhanced resistance to volume changes and improved shear strength under cyclic wet-dry conditions. Moreover, crack development is inhibited in LS-modified soil. LS decreases the soil's affinity for water by creating a hydrophobic barrier around soil particles. Furthermore, the interaction between LS and the layered clay minerals results in stronger binding, which contributes to the stabilization process. The findings indicate that LS not only reduces the swelling nature of expansive soils and improves their shear strength and stability under wet and dry cycling conditions, but also provides an environmentally friendly solution for soil stabilization and sustainable construction practices.