Friction Stir Welding (FSW) is one of the best choices of joining light weight metal structures involving lap joints as conventional welding methods find difficult in getting sound weld joints. Aluminium alloys are lightweight materials relatively used in space frame structures, ship buildings and panels of automotive vehicles. Main objective of this research is to investigate Al-SiC FSW lap joints and to examine the suitable pre-fill nanoparticles in the configured grooves to augment the weld strength. Three different volume additions of SiC nanoparticles and tool rotational speed were considered to fabricate lap joints for the investigations. Tool rotational speed and volume of SiC reinforcement have a significant impact on the dissemination of SiC in the weldment and weld quality. The spread of SiC nanoparticles in the weld area strongly affects the weld microstructure and mechanical characteristics. Nano SiC filled lap joint has shown a significant improvement in mechanical properties as compared to a joint without nanoparticles. The best lap joint is achieved with 20 vol% of SiC and 1500 rpm of rotational speed. The investigations imply that the tensile strength is decreased for joints with 26 vol% of SiC, due to clustering of reinforcement particles. The supplement of SiC nanoparticles restricts the growth of grains and refines the stir zone (SZ) microstructure and hence this method of weld process is recommended for lap weld joints in metal structures.