Lightweight metal–matrix nanocomposites (MMNCs) (metal matrix with nanosized ceramic particles) can be of significance for automobile, aerospace, and numerous other applications. It would be advantageous to develop effective nanomanufacturing methods for fabrication of bulk components of aluminum based MMNCs through solidification processing. However, it is extremely difficult to disperse nanosized ceramic particles uniformly in molten aluminum. In this paper, a high power ultrasonic probe is used to disperse nanosized SiC particles into molten aluminum alloy A356. Experimental results show that the ultrasonic cavitation based dispersion of nanoparticles in molten aluminum alloy is effective. The uniform nanoparticle dispersion in the Al alloy matrix resulted in significantly improved mechanical properties. To enhance the nanomanufacturing efficiency, various nanoparticle feeding techniques were explored and experimental results are presented.