With the increasing use of Metal Matrix Composites (MMC) in advanced industries, various methods of manufacturing parts made of these composites have been re-considered. One of these methods is the use of high-power ultrasonic technology in the casting process (ultrasonic melt processing). For this purpose, in the present study, the effect of applying ultrasonic vibrations on the casting of aluminum alloy 6061 and Al6061/SiC MMC has been investigated. The ultrasonic melt processing has been carried out in two modes with and without applying ultrasonic vibrations for the two mentioned materials. Also, the effect of the time of ultrasonic melt processing (1 and 2 min) on the output parameters including hardness, compressive strength, grain size, and distribution of SiC reinforcing particles were investigated. At the same time, the effect of reinforcing particles (SiC) and ultrasonic melt processing independently was also investigated in various tests. The results showed that in both the Al6061 and Al6061/SiC, the application of ultrasonic vibrations caused the creation of a fine-grained structure in the casting (50% reduction in grain size) and as a result, the hardness (20% increase in hardness) and compressive strength of the sample increased. Also, in the metal composite (Al6061/SiC), the ultrasonic melt processing caused a finer and more uniform distribution of SiC particles in the base aluminum material. These phenomena were attributed to the effect of cavitation and acoustic streaming in the melt.