Abstract: This study investigates the development of weld nugget and Heat Affected Zone (HAZ) in Resistance Spot Welding (RSW) using numerical simulation approach and experimental process. The finite element modeling technique known as SYSWELD was utilized for the simulation process. In the simulation process, a two dimensional axis-symmetric finite element model using customized electrode meshing modeling was chosen to develop the thermal-mechanical-electrical characteristic of the spot weld. The model was developed for welding of two and three sheets of 1 mm thick low carbon steel by flat-faced copper electrodes. The RSW simulation parameters such as force, weld current, weld time and the temperature distribution of the welded sheets and electrodes used were taken into consideration throughout the study. For the experimental verification, an actual welding by RSW with similar welding parameter was carried out. The formation of spot weld nugget and HAZ, based on the common welding parameter for simulation and experiment were compared and discussed. It was found that the theoretical radius of weld nugget and HAZ developed by finite element method are accurately correlated with the results of the experiment.