The application of graphene nanoplatelets (GNPs) and multi-walled carbon nanotubes (MWCNTs) as a thin interlayer between the faying surfaces of AISI-1008 steel joints and its effect on the microstructure and mechanical properties of the welded joints has been reported here. The resistance spot welding (RSW) technique has been utilised to entrap the nanoparticles in the weld nugget. Single lap shear tests were performed to get an insight into the weld strength of the bare, GNPs, and MWCNTs interlayered samples, and ~49% and ~45% enhancements respectively were reported. Fracture surface morphology depicted that a combination of both brittle and ductile fractures were the major causes of failure. A detailed microstructural study was performed using light microscopy, SEM, TEM, XRD, and Raman spectroscopy for both cases. The increase in the weld strength and hardness of the nanocomposite formed at the weld nugget was attributed to grain refinement and numerous strengthening mechanisms.