Although 2-dimensional (2D) design methods have been shown to work well in defining the longitudinal reinforcement layout in geosynthetic-reinforced soil (GRS) bridge abutments, three-dimensional (3D) effects may play a role in the design of the side walls and the associated transverse reinforcement layout. The objective of this study is to understand the deformation behavior of GRS bridge abutments considering 3D boundary effects, using finite difference analyses to simulate the deformation behavior of a hypothetical GRS bridge abutment expected during construction. Soil-concrete and concrete-concrete interactions were simulated using interface elements and soil-geogrid interactions were simulated using geogrid structural elements. Analyses were performed in stages to simulate the abutment construction process with different reinforcement vertical spacing and length. The results presented in this paper provide insight into the lower wall lateral facing displacements in both the longitudinal and the transverse directions, as well as bridge seat settlements at different sections. This information is a useful component in the development of comprehensive design guidance for GRS bridge abutments.