Soil improvement is commonly carried out in construction work with the aim of increasing the bearing capacity / strength of the soil so that it can carry the construction load that will stand on it. The method that is often used is soil stabilization with the addition of stabilization materials. In this study, soil stabilization was carried out with the addition of Portland Cement. Initially, the process involved gathering soil samples and conducting laboratory tests to assess the soil's physical and mechanical characteristics. Subsequently, the soil samples were prepared to undergo Unconfined Compressive Strength (UCS) testing, employing three different proportions of cement: 5%, 10%, and 20%. The findings indicated that the soil specimen possessed a moisture content of 97.13%, a specific gravity of 2.51, a liquid limit of 33.80%, and a plasticity limit of 22.52%, resulting in a plastic index value of 11.28%. According to the USCS (Unified Soil Classification System) method, the sedimentary soil was classified as CL (Clay-Low), representing clay soils with low plasticity values. Unconfined compressive strength testing on sedimentary soil samples without portland cement obtained a compressive strength. Unconfined compressive strength testing was conducted on sedimentary soil samples in the absence of Portland cement, yielding a compressive strength value of 0.352 kg/cm2. Conversely, when the soil was stabilized with varying proportions of Portland cement, the highest compressive strength value of 14.45 kg/cm2 was observed in the soil sample mixed with 20% cement and subjected to a 28-day curing period. The outcomes demonstrate that the Unconfined compressive strength of sedimentary soil dredged from Bili-Bili Dam, when stabilized with Portland cement, exhibits an inclination towards increased load-bearing capacity and strength as the percentage of cement and curing time are augmented. With this enhanced strength, the soil can be categorized as having a firm consistency suitable for constructing structures and road base soils.