Bond deterioration is one of the major consequences of reinforcement corrosion in reinforced concrete (RC) structures. In this paper, a two-phased numerical modelling approach is presented that aims to determine the constitutive behaviour (bond–slip) at the reinforcement-concrete interface at a certain corrosion level. The novelty of the approach is that it consists of a crack model and a bond model, and that the flow of corrosion products into the pores and corrosion-induced cracks as well as the effect of the bonded length and concrete cover are taken into account in the 2D crack model. The resulting expansion of corrosion products from the crack model is used as input in the 3D bond model. The combination of both models leads to a procedure that balances computational time and modelling detail. The model is validated on a substantial amount of experimental pull-out test results. A good agreement is obtained between the experimental data and the models for different corrosion levels in terms of crack width, crack pattern, corrosion-induced bond loss, and failure mode.