This study examines how variations in the thickness of the Expanded Poly-Styrene (EPS) core within sandwich panels influence the axial load-carrying capacity of Precast Concrete Sandwich Panels (PCSP), which are used as infill walls in building structures. A Finite Element Analysis (FEA) approach is used to simulate the behaviour of PCSP by incorporating material properties, boundary conditions, and geometric configurations to accurately represent the behaviour of the sandwich panel based on experimental observation. Parametric studies were performed to evaluate the effects of different EPS core thicknesses specifically 60 mm, 80 mm, and 100 mm on out-of-plane displacement and axial load-carrying capacity. The result shows that the variation in EPS core thickness has no significant effect on out-of-plane displacement and the load-carrying capacity of the PCSP. This study enhances sustainable building practices by deepening the understanding of the factors that affect the performance of sandwich panels with an EPS core. Additionally, it facilitates the construction of more efficient infill walls designed for regions susceptible to seismic loads.