In this investigation, alumina (Al₂O₃) nanoparticles were utilized to study the mechanical properties of two polymer nanocomposite systems applied to low-carbon steel substrates. The nanocomposites comprised polystyrene (PS) and polymethylmethacrylate (PMMA) matrices, each incorporating 5 wt.% Al₂O₃ nanoparticles. Tensile tests revealed that the nanocomposites exhibited superior mechanical performance compared to pure polymers. For PMMA-Al₂O₃, tensile properties such as elastic modulus (E), ultimate tensile strength (σₐᵤₗₜ), and strain (eᵤₗₜ) were 2.6326 GPa, 44.52 MPa, and 0.02560, respectively, showing improvements of 16.5% in σₐᵤₗₜ and 33.7% in eᵤₗₜ. Similarly, PS-Al₂O₃ showed σₐᵤₗₜ and eᵤₗₜ improvements of 19.1% and 61.5%, respectively, compared to pure PS. The Scanning electron microscopy (SEM) revealed flocculation and uneven nanoparticle dispersion. At low magnification (1.56 µm), PS-Al₂O₃ particles were well-separated, while higher magnification (11.6 µm) showed aggregation. The average nanoparticle diameters for PMMA-Al₂O₃ and PS-Al₂O₃ were 201.1 nm and 184.6 nm, respectively. Flocculation and low-density interphase, attributed to fewer polymer chain anchoring sites on Al₂O₃ surfaces, reduced the elastic modulus. These findings emphasize the need for advanced blending techniques to achieve uniform nanoparticle distribution and improve polymer-nanoparticle interfacial bonding. Optimized dispersion methods are crucial for enhancing the mechanical properties of Al₂O₃-reinforced nanocomposites.