Select MAX phase-based ceramics were screened with respect to their potential susceptibility to environmentally-assisted degradation in an oxygen-poor liquid lead-bismuth eutectic (LBE) environment, both under static and fast-flowing exposure conditions. The majority of the MAX phases exposed to oxygen-poor (CO ≤ 2.2 × 10−10 mass%) static liquid LBE for at least 1000 h at 500 °C showed exceptional chemical compatibility with the heavy liquid metal, i.e., no evidence of LBE dissolution attack was observed, despite the absence of a continuous oxide scale on the surface of the exposed MAX phase ceramics. The local LBE interaction observed only with the Zr-rich MAX phases consisted in the partial substitution of Al by Pb/Bi in the MAX phase crystal structure and the in-situ formation of Pb/Bi-containing solid solutions. Moreover, the interaction of Zr-based MAX phases with static liquid LBE was accompanied by the dissolution of parasitic intermetallic phases, which facilitated the further LBE ingress into the ceramic bulk. The erosion resistance of select MAX phase ceramics was also assessed in oxygen-poor (CO ≈ 5 × 10−9 mass%) fast-flowing (v ≈ 8 m/s) liquid LBE for 1000 h at 500 °C. Despite the moderate LBE oxygen concentration, oxidation was the predominant corrosion mechanism, while no erosion damages were observed in the exposed MAX phase ceramics. The resistance of the MAX phase ceramics to both dissolution corrosion and erosion in contact with oxygen-poor static and fast-flowing liquid LBE, respectively, was compared to that of the 316L reference structural stainless steel.