The impact of SiO₂ nanoparticle concentration on the structure and mechanical characteristics of polystyrene-based polymer nanocomposites was examined. PS+SiO2 nanocomposites were made using the solution mixing techniques. The crystalline structure of the polymer was not substantially changed by the addition of SiO2 according to XRD patterns. According to tensile test the addition of the 1 wt% SiO₂ nanoparticles into the polymer leads to raise the tensile strength from 14.05 MPa to 15.48 MPa. Conversely, as the amount of SiO2 nanoparticles increased, the elongation at break decreased. The observed mechanical behavior was attributed to interfacial interactions and the dispersion state of SiO₂ nanoparticles, where well-dispersed particles enhance load transfer, while agglomeration at higher concentrations reduces deformability.