This paper attempts to predict the cleavage fracture probability for a low-alloy bainitic steel. Fractographic analysis of broken compact tension (CT) and Charpy V-notch (CVN) specimens was performed. An evolution of physical mechanisms of cleavage initiation was found: cracked-particle-induced cleavage was observed at low temperature, whereas a plasticity-induced mechanism was assumed as temperature increases. To take into account these observations, temperature-dependent Weibull parameters were used in the Beremin model. The introduction of a threshold cleavage stress was necessary to account for the skewness of the fracture probability distribution. With these parameters identified on the instrumented Charpy data set, the fracture toughness J(c) was successfully predicted in the DBTT range.