Metal matrix nanocomposites (MMnCs) comprise a metal matrix filled with nanosized reinforcements with physical and mechanical properties that are very different from those of the matrix. In ZA-27 alloy-based nanocomposites, the metal matrix provides ductility and toughness, while usually used ceramic reinforcements give high strength and hardness. Tested ZA-27 alloy-based nanocomposites, reinforced with different types (SiC and Al₂O₃), amounts (0.2 wt.%, 0.3 wt.%, and 0.5 wt.%) and sizes (25 nm, 50 nm, and 100 nm) of nanoparticles were produced through the compocasting process with mechanical alloying pre-processing (ball milling). It was previously shown that the presence of nanoparticles in ZA-27 alloy-based nanocomposites led to the formation of a finer structure in the nanocomposites matrix and an improvement in the basic mechanical properties (hardness and compressive yield strength) through the enhanced dislocation density strengthening mechanism. Solid particle erosive wear testing demonstrated that these improvements were followed with an increase in the erosive wear resistance of tested nanocomposites, as well. Additionally, by analyzing the influences of type, amount, and size of nanoparticles on the erosive wear resistance of nanocomposites, it was demonstrated that there is an optimal amount of nanoparticles, which in our case is 0.3 wt.%, and that the presence of SiC nanoparticles and smaller nanoparticles in nanocomposites had more beneficial influence on erosive wear resistance.