B4C–CeB6 composites were prepared via hot pressing using CeB6 powder as an additive and with varying CeB6 contents ranging from 0 to 5 vol%. The effects of CeB6 content on the microstructure, mechanical properties, and tribological properties of the composites were investigated. The introduced CeB6 did not participate in any chemical reactions during sintering and existed only as a second phase in the B4C matrix. When the volume fraction of the added CeB6 was less than or equal to 1 %, the second phase was uniformly distributed in the matrix, which refines the B4C grains. The high thermal conductivity of CeB6 facilitates efficient heat transfer, contributing to the formation of densely sintered bodies. Additionally, the residual stress at the grain boundary resulting from the difference in the thermal expansion coefficients of the two particles promotes crack deflection and branching, thereby enhancing the toughness of the composite. When the CeB6 content is 1 vol%, the composite exhibits optimal comprehensive mechanical properties, with the density, Vickers hardness, flexural strength, and fracture toughness reaching 99.49 %, 31.57 GPa, 643.2 MPa, and 4.27 MPa m1/2, respectively. In the dry reciprocating friction test, the wear rate after a 30-min sliding test used an Al2O3 ball under a load of 15 N was only 0.98 × 10−6 mm3 N−1 m−1. These comprehensive properties make B4C–CeB6 composites very attractive candidates for various applications.