When mechanical milling technique is used as a production method of metal matrix composites (MMCs), the problem of excessive work hardening adversely affecting product properties is observed, whereas the composites with homogeneous particle distribution without the use of further milling times in a ball mill can be fabricated by a new method called "flake powder metallurgy." In this study, B4C nanoparticle-reinforced Al-Cu-Mg alloy matrix nanocomposites (MMCs) were produced by flake powder metallurgy method. The effect of flake powder metallurgy on the morphology, particle size, apparent density, nanoparticle distribution, density and hardness of B4C nanoparticle-reinforced Al-Cu-Mg alloy matrix composites was investigated. Flake powder metallurgy was assisted by using a short-term ball milling, which resulted in improved homogeneity of the B4C nanoparticle distribution. For fine Al-Cu-Mg matrix powders (FNP group) and 1 h of flake time, as the B4C nanoparticle content gets smaller from 1 to 5 wt%, density reduces from 2.7733 to 2.7350 g/cm(3) and hardness increases from 117.11 to 125.21 BHN. Moreover, as the initial particle size of Al-Cu-Mg alloy matrix increases, density and hardness decrease due to agglomeration effect.