This paper introduces a novel technique to enhance the efficiency of cement stabilisation for expansive soil by adding a recycled waste material known as eggshell powder. Expansive soils pose significant challenges in construction and geotechnical engineering due to their high swell-shrink potential, resulting in undesirable volume changes. By incorporating eggshell powder into the cement stabilisation process, this paper explores the potential to improve the performance of expansive soil treatments. Eggshell powder, readily available as a by-product of the food industry, offers promising characteristics such as its chemical composition and particle size distribution. It contains calcium carbonate and is ideal for stabilising expansive soil. The powder is made by cleaning, sterilising, and grinding the eggshells. Various geotechnical tests, including compaction characteristics, California Bearing Ratio (CBR), swelling ratio, and direct shear tests, were conducted to assess the performance of the treated soil. The results indicate that adding eggshell powder to cement significantly enhances the engineering properties of the stabilised soil. The maximum improvement in unsoaked CBR and direct shear strength was achieved when 6% eggshell powder was added to 6% cement. Moreover, the research findings highlight the efficacy of the eggshell powder–cement soil treatment method in mitigating soil swelling compared to the eggshell powder-treating approach. Incorporating eggshell powder in cement improves the stabilised soil’s mechanical characteristics and provides an effective solution for controlling soil swelling, thereby enhancing the overall stability and performance of geotechnical structures.