The main subject of the paper is the analysis of plastic flow of tailored blanks in deep drawing processes. It has been shown in the present study that the key issue of the discussed problem is the development of a method which would allow to analyse nonuniform flow of blanks characterized by large changes of geometry, strain and stress state in the deformation process. Estimation of the formability of a tailored blank is not possible taking into account only the formability of the component sheets, without considering the shape of the drawn part as well as the location and orientation of the weld line with respect to directions of principal stresses in the blank. The present paper presents a model of tailored blanks which can be used in a finite element simulation to determine the formability of such blanks. The proposed solution makes use of the results obtained in experimental tests on tailored blanks. The relationship between the formability of the base material and the formability of the weld zone has been found. Model parameters can be determined from the characteristics of the component sheets and properties of the welded zone. Numerical simulation was carried out using the developed model. It was found that the flow of a tailored blank depends on the orientation of the weld line with respect lo the directions of principal stresses and the formability of a tailored blank depends on the characteristics of the component sheets and the quality of the weld. Theoretical model of a tailored blank and numerical simulation have been validated by experimental tests. Local strains from numerical simulation have been presented on the forming limit diagrams and compared with strains measured in experiments.