The resistance spot welding is one of the most commonly used methods of jointing metal sheets that has several applications in different industries such as aviation, home appliances and especially automotive. Because of its widespread application in automobile production lines, the quality control and welds testing are very important issues. Tensile test is one of the quality control techniques in this type of welding. The main purpose of this work was to predict ultimate strength of the sheets welded by resistance spot welding. Therefore, this process was simulated using ABAQUS commercial finite element package for DP1000 dual phase steels. A coupled electrical-thermal simulation was first run in order to predict the temperature distribution throughout the sheets. The temperature distribution history was then imported into a structural analysis in order to predict the residual stresses within the sheets. The size of nugget and heat-affect zone were also predicted through the history of temperature at the sheets contact point. The effect of process parameters, e.g. electrical current and applied load, on the nugget size was also predicted by the simulations. In order to predict the ultimate strength of weld joint, the modified Gurson damage model was employed to simulate uniaxial tension of the welded sheets in ABAQUS. The model was divided into welt spot, heat-affected zone and base metal partitions. The weld spot partition was joined through tie constraint in ABAQUS. Different sets of material parameters for the model was assigned to each partition. The residual stress was also imported from the previous analysis as the initial stress into the new model and the uniaxial tension was simulated. The force-displacement curve in uniaxial tension was predicted using the model and then compared with that of experiment. A fairly good correlation was observed between the simulated and experimental results. Finally, the effect of electrical current amplitude, weld time and applied load on the weld strength was studied through simulation. By increasing the electrical current, the size of nugget also increased and this resulted in nugget strength. By increasing the weld time, the produced heat in contact surface also increased and resulted in a larger nugget and higher strength of the nugget. A large applied force by electrodes caused a large contact surface and higher residual stresses in the nugget and sheets which finally resulted in decrease of strength of the nugget and damage initiation at lower force. Keywords: Resistance spot welding, Finite element simulation, Residual stress, Modified Gurson damage, Tensile test.