Abstract: In this study, 3 wt% TiB₂/A356 composites were successfully synthesized via a salt-metal reaction method to investigate the influence of the rare earth element, cerium (Ce), on their microstructure and mechanical properties. Ce was introduced in varying mass fractions through the addition of an Al-Ce intermediate alloy. The findings indicate that Ce promotes a more uniform dispersion of TiB₂ particles within the A356 matrix. Additionally, the presence of Ce, alongside TiB₂ particles, contributes to the refinement of α-Al grains and the modification of eutectic Si. The optimal mechanical properties were observed with the addition of 0.3 wt% Ce. Specifically, the composites demonstrated increases in yield strength, tensile strength and elongation by 9.2%, 11.5% and 57.1%, respectively, compared to the composites without Ce. The analysis suggests that Ce enhances the dispersion of TiB₂ particles by improving wettability and interfacial stability between TiB₂ and the matrix, and the modification of eutectic Si is attributed to increased constitutional undercooling due to Ce segregation, which leads to the formation of Ce-containing nanoscale precipitates within the eutectic Si, thereby inhibiting Si growth.