Aluminum alloy 5083 has low density, mechanical properties, high corrosion resistance, and high welding capability. Due to high thermal conductivity, specific heat, and latent heat, as well as the relatively high coefficient of thermal expansion of aluminum, achieving a connection with good mechanical properties is always very important. This study aimed to investigate nanoparticles’ surprising and unexpected effects in forming various microstructures, which directly improve the mechanical properties of the welding process as a new and surprising idea. The effects of siliconized Zn-graphene oxide complex nanoparticles on weld geometry, mechanical properties, and microstructure of AA5083 were investigated. The gas metal arc welding process welded the samples, and different amounts of nanoparticles were investigated. The results reveal that utilizing nanoparticles can be affected by the weld geometry and the properties of weld metal. 0.25 g of nanoparticles had low face reinforcement, and the bead width and penetration depth dramatically increased. The presence of nanoparticles inside the molten zone and its effect on grain size improved mechanical properties, according to the Hall–Petch relationship. The ultimate tensile strength and yield strength of the S0.25 sample increased by 58.24 and 28.28%, respectively, compared to the welded sample without the presence of nanoparticles. Also, the ductility of this sample during the failure test showed that elongation increased by 36.75%.