In the present study, the effect of the nanosized SiC particles loading and Mg addition on the characteristics of Al/SiC composite powders produced via a relatively new method called in situ powder metallurgy (IPM) was investigated. Specified amounts of SiC particles (within a size range of 250 to 600 mu m) together with SiC nanoparticles (average size of 60nm) were preheated and added to aluminum melt. This mixture was stirred via an impeller at a certain temperature for a predetermined time. The liquid droplets created by this process were then subsequently cooled in air and screened through 250 mu m sieve to separate micron-sized SiC particles from solidified aluminium powder particles containing nanosized SiC particles. Results of SEM and TEM studies together with microhardness measurements revealed that the commercially pure (CP) Al could not embed as-received SiC particles. However, the nanosized particles were distributed uniformly in the Al-1wt% Mg powders. The process yield and microhardness of the Al-1Mg composite powders increased with increasing the contributed amount of nanosized SiC particles.