Reinforced concrete (RC) structural walls are widely used in high-rise buildings as the lateral force resisting system because of their inherent economy, stiffness, and strength. The floor plan configuration of residential buildings in Chile consists mainly in assemblies of large longitudinal walls and shorter transverse walls coupled by floor slabs. The coupling effect of the slabs has affected the response and the observed damage of RC buildings in recent earthquakes. The main objective of this article is to assess the seismic response of a RC structural wall building with coupling slabs. Additionally, the effect of the amount of slab reinforcement on the seismic response of the building is evaluated. To achieve the proposed objectives, seven three-dimensional models of a case study building were developed using shell-type elements in DIANA. The first four models aim to evaluate the effect of using elastic slabs with reduced (i.e. cracked) moment of inertia. The last three models consider nonlinear behavior for both walls and slabs. The response of the building was estimated using nonlinear static analysis and the seismic performance is evaluated from the results of roof displacement and shear, moment, and axial forces of the walls. Additionally, the seismic performance is evaluated from the strain demands of concrete and steel in both walls and slabs. Relevant conclusions about the building behavior, slab demands, and failure mode are drawn.