Magnesium-based alloys were more prevalent in automobile applications owing to their mechanical properties, low mass, and density. However, its poor mechanical properties are restricting its applications. Therefore, the present study focuses on improving the mechanical properties of AZ31D alloy by reinforcing silicon carbide (SiC) and graphite (Gr) nanoparticles with weight fractions of 2%, 4%, and 6% using stir-casting technique. The microstructure analysis was performed using a scanning electron microscope. The elemental analysis was confirmed using energy-dispersive spectroscopy, and X-ray diffraction was used to study various phases in the nanocomposites. Further, the mechanical properties, such as microhardness, ultimate tensile strength, yield strength, and compression strength of the nanocomposites, were significantly improved by 53%, 59%, 62%, and 82%, respectively, as compared with base alloy.