<p>A non-destructive method for determining residual welding stresses (RWS) is proposed, which is based on the combined application of the ultrasonic wave method (US method) and electronic speckle interferometry method (ESPI method). The scientific foundations of the proposed method are based on the condition of equality of the areas of the compression and tension portions of the RWS diagram. Several variants of the method implementation have been developed, which can be used to determine RWSs in the welded joints of full-scale structures, taking into account the peculiarities of stress-strain states in aluminum alloys and structural steels. The method was evaluated to determine the longitudinal (along the weld) component σ_x of RWS in specimens of butt joints made of 1561 aluminum alloy and 09G2S low-carbon steel. Satisfactory reliability of the obtained values of tensile RWSs in the weld zone of welded joints of experimental specimens was established. The method can be used to determine RWSs in full-scale welded structures during their manufacture and operation.</p>