Plastic waste is an ongoing environmental issue that significantly increases land and marine pollution on a worldwide scale. This study investigated the possibility of stabilizing silty clay soil using discarded plastic materials such as nylon fibers from waste fishing nets. Silty clay is an expansive soil renowned for its low plasticity, low permeability, and high-water retention capacity. Given the right planning, compaction, and stabilization, silty clay soil can hold up a variety of roadway constructions. Moreover, the inclusion of waste nylon fibers from waste fishing nets exhibits high tensile strength and elasticity, leading to a decrease in the soil’s compressibility and brittleness. The researchers used various tests to bearing capacity (CBR), unconfined compressive strength (UCS), and the undrained shear strength (UDS) of a silty clay soil treated with three ratios (0%, 0.25%, 0.60%) of waste nylon fibers. The researchers’ findings indicated that stabilization of a silty clay soil with the application of nylon fibers from waste fishing nets improved the UCS and UDS of the stabilized silty clay soil and was found to be 109.02% at the inclusion of 0.25% waste nylon fibers. Results from the CBR indicated that the inclusion of 0.25% waste nylon fibers in silty clay soils increased the bearing capacity of the soil by 62.68% and decreases at 0.60% waste fiber content. Therefore, nylon fibers from waste fishing nets can be efficiently used as a stabilizing agent at optimal contents to improve the strength properties of the silty clay soil as a subgrade foundation for roadway projects.