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Hot tearing is a severe solidification defect that occurs during the metal solidification process. To reduce the hot-tearing susceptibility (HTS) of a 5TiB2/Al-5Cu composite, rare-earth Ce with mass fractions of 0.2%, 0.5%, and 1% was added to the composite in this study. The results indicated that the HTS of the composite decreased with the increase of Ce from 0.2% to 1%. The HTS value of the 5TiB2/Al-5Cu composite decreased from 15.61 to 5.60, and the solidification-temperature range of the composites gradually narrowed after the Ce addition. In addition, the grain size of the composite was refined, and the average grain diameter decreased from 26.29 μm to 18.97 μm. With the increase in Ce content, the composite microstructure was refined and the TiB2 particle agglomeration dissolved. As the Ce increased, the finer lamellar Al8Cu4Ce phase promoted a more uniform microstructure and a more fluid liquid metal. Therefore, the residual liquid metal better fed the cracks, and the grain-boundary phases formed more bridges to improve the high HTS of 5TiB2/Al-5Cu composites.