Summary: The construction of slip-line fields for a centre crack in a tensile panel with a mismatched welded joint will be discussed, from which expressions of the limit load and the constraint state around the crack tip will be derived in an analytical formulation. Based on these solutions the crack driving force of a structure with a cracked mismatched welded joint can be predicted using the procedure of ETM-MM (Engineering Treatment Model extended for mismatched cracked structures). The theoretical solutions have been verified by two-dimensional finite element calculations.