This paper presents an experimental study on resistance spot welding of DP and TWIP steel sheets used in automative industry. A timer and current controlled resistance spot welding machine having 120 kVA capacity and a pneumatic application mechanism with a single lever was used to prepare the specimens. Welding periods were chosen as 5, 10, 15, 20, 25 and 30 cycles (1 cycle = 0.02 s) and also welding currents were increased from 6.33 kA up to 15.7 kA in steps of 0.9 kA. The electrode force was kept constant at 4 kN. The prepared welding specimens were exposed to tensile-peel test and micro and macro-structures of specimens were investigated by means of an optical microscope and scanning electron microscope (SEM) in order to see the joinability of DP and TWIP steel sheets by resistance spot welding. Finally appropriate welding current and time were advised to the users.