This paper presents a three-dimensional simulation method for chloride ingress that considers the influence of concrete mesostructure. In addition to the procedures introduced for improving simulation, a comparison with the two-dimensional approximation is presented to demonstrate the necessity of three-dimensional simulations. The use of a two-dimensional approximation may result in the underestimation of the severity of chloride ingress and the overestimation of the influence of material heterogeneity. Therefore, it cannot replace the need for a three-dimensional simulation, especially in the case of chloride ingress.