In some Generation IV reactor configurations, embrittlement of the liquid metal can manifest in various forms, and this behaviour strongly depends on the specific solid–liquid couple. For the ALFRED demonstrator, which will be built at the RATEN ICN site in Romania, the study of embrittlement induced by molten lead in 316L stainless steel at temperatures of 350–450 °C is of interest. The purpose of the paper is to evaluate the effect of liquid metal embrittlement on the fracture mechanics properties of 316L tested in liquid lead. To do this, the “Normalisation Data Reduction Technique” (ASTM E1820) is used to obtain the J-R resistance curve for 316L steel in molten lead. In this way, the fracture mechanics parameters were obtained, indicating the fracture toughness of 316L steel in liquid lead with a saturated oxygen concentration at 350 °C. Optical and SEM examinations complement the analyses.