Farming residues like eggshells and Sea residues like seashells have turned into a well-known choice for enhancement of soft soils because of their expense viability and natural cordiality, making them a suitable choice for accomplishing sustainability in the construction sector. Soft clay soils have relatively low bearing capacity and high consolidation settlement. For this reason, the construction of the subgrade in soft clay soils has met many obstacles. Expensive and traditional solutions are utilized in some projects, which usually encourage the idea of removing and replacing soft soils. Instead, land improvement is lately the best way to solve this problem. This paper aims to decrease the use of lime as the most common stabilizers utilized for soft soils; use recycled waste materials like seashell and eggshell powder is the novel objective of this study. California bearing ratio tests were conducted to examine some changes in the engineering properties of treated soils with waste seashell and eggshell powder with different percentages (2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18% and 20%) by dry weight of soil. The results show the inclusion of seashell and eggshell powder increased the CBR ratio of soft clay soil. The influence of adding seashell powder on soft clay soil is more effective than eggshell powder in road construction but finally, both of them can be used as a waste natural stabilizer to increase the CBR ratio of soft clay soil.