Variations of surface residual stresses with subsequent weld passes were investigated in API 5L X70 steel plates by the magnetic barkhausen noise (MBN) technique. The plates were welded by applying a number of different passes under fully clamped conditions. After each weld pass, the MBN signal and hardness distributions on the front and back surfaces of the plates were measured. A specific calibration procedure and setup were used for conversion of the MBN signals into elastic stress values. The results were analyzed by considering microstructure investigations and hardness measurements, and then the results were compared with the results of X-ray diffraction measurements. MBN measurement after appropriate calibration seems to be a good candidate for rapid nondestructive monitoring of the variation of surface residual stresses in welded components. Moreover, it might provide critical data for computer simulation and weld process design, leading to a higher performance and longer life in service by controlling the residual stress state.