In the present work, the finite element method is used to calculate the J integral and the size of the plastic zone at the interfacial crack tip in ceramic/metal bimaterials in mode I and mixed mode. The plastic behavior of the stress–strain curve of the metal is approximated by a Ramberg–Osgood function and the ceramic has a linear elastic behavior. The plastic properties effects of metal and the crack length were highlighted as well as the effect of the metal thickness on the variation of the J integral at the crack tip.