Ce-CLAM specimens were exposed to lead-bismuth eutectic (LBE) for 1500 h under 10−6 wt% oxygen concentration at 500 °C. The continuity and integrity of the oxide scale were better in Ce-CLAM specimens than in CLAM specimens, and the parabolic rate constant kp of oxide scale growth was only about 1/2 that of CLAM specimens. Ce-CLAM specimens exhibited better LBE corrosion resistance compared with CLAM specimens, which was mainly attributed to the inhibition function for Fe out-diffusing and the improvement for grain boundaries from Ce. A model was proposed to illustrate the mechanism of Ce-CLAM’s LBE corrosion resistance. •Ce can improve the LBE corrosion resistance of CLAM specimens.•Ce mainly segregates at grain boundaries, especially triple junctions.•There are less M23C6 precipitates at grain boundaries in Ce-CLAM specimens.•Ce have a hindering effect on the outward diffusion of Fe.•A model is proposed to explain the improving mechanism from Ce.