In this paper, the microstructural characteristics of the interface in a bimetallic aluminum composite with a regular 3D lattice copper preform produced by squeeze casting are numerically analyzed. To this end, the effects of three variables—the wall thickness of the lattice copper preform, the pouring temperature of the aluminum melt, and the squeeze pressure—on the interface thickness, eutectic cell thickness, and θ-phase thickness were investigated. An L15 orthogonal array was used for the experimental design, with all three independent variables set at three levels with equal spacing. Numerical regression analysis, analysis of variance (ANOVA), and main and interaction effect functions using surface plots were employed to demonstrate the effects of the variables. The interface microstructure was examined using optical and electron microscopes equipped with image analysis and EDS. The results indicate that the interfacial microstructure of the composite consists of four layers: pure copper, the θ phase, the α+θ eutectic, and the aluminum α phase. The preform thickness is the most influential factor affecting the thickness and morphology of the intermetallic compounds at the interface, followed by the pouring temperature and squeeze pressure. For the preform thickness parameter, the highest and lowest data points for both the eutectic cell thickness and θ-phase thickness responses were obtained at the 0.75 mm and 1.25 mm levels, respectively. As the preform thickness increased from 0.75 mm to 1.25 mm, the average data for the eutectic cell thickness response decreased by 45.2% and for the θ-phase thickness by 58.3%.