In this work, effect of tool speed and direction of tool rotation of friction stir welding (FSW) process on the cast MMC is analyzed. Aluminum 6061 alloy reinforced with 20% silicon carbide particles added with 2% molybdenum disulphate is prepared by die casting process. Macro and micro-structural analysis is performed to study the size and shape of the constituents, to discover the defects associated with stir welding and quality of weld. Micro-hardness observations are carried out on the parent metal, FSW zone and heat affected zone. It is observed that FSW with high speeds develops higher hardness and most of the higher hardness value occurs in in the order of FSW welding zone, center zone and heat affected zone, and also hardness value of clockwise tool rotation is greater than anti-clockwise tool rotation.