In this study, fracture behavior of welded ductile iron was investigated experimentally and theoretically. Ferritic ductile irons were joined by cold arc welding method by using the nickel base electrode. In experimental part of the study, firstly, mechanical and metallographical properties of the welded specimens were identified. Then, J- Integral toughness values were determined by fracture toughness tests for different crack locations including base metal, heat affected zones and weld metal. In numerical part of the study, finite element analyses were conducted by fixing 3- D models precracked on different locations. After stress – strain analyses, stress triaxiality and plastic deformation characteristics around crack tip were determined for each crack locations and different crack sizes. It was found that stress triaxiality and plastic strain values increase with growing crack length. Different regions with different strength levels, affect the extension of plastic deformation in the models. Hindrance on the extension of plastic deformation at HAZ and diffusion line causes extra increase in stress triaxiality at crack tip.