<p>In recent years, the increasing performance requirements of growing engineering systems have driven the need for advanced materials with superior strength-to-weight ratios. By incorporating lightweight metal matrix composites into crucial parts, substantial fuel consumption and related emission reductions may be accomplished, supporting sustainable engineering methods. This study reports fabrication of A356 matrix hybrid nanocomposites reinforced with varying weight percentages (1–5 wt.%) of boron carbide (B₄C) and a fixed 1 wt.% zirconium dioxide (ZrO₂) via ultrasonic vibrations assisted two-step stir casting. The microstructure, mechanical properties, and tribological performance of the A356–B₄C–ZrO₂ composites were evaluated. The microstructure analysis revealed well‑distributed nano reinforcement particles promoting grain refinement. The microhardness and ultimate tensile strength increased by 50% and 51.7%, respectively, compared to the base matrix. The fractured surfaces of hybrid nanocomposites were examined with a scanning electron microscope to analyze the fracture behaviour. The hybrid nanocomposite exhibited reduced wear rates and friction coefficients compared to the base metal.</p>