The constitutive models have an important role in understanding the thermo-mechanical behavior of concrete and predicting its durability under fire loading. In this paper, the authors have developed a new constitutive temperature-dependent model for rubber concrete based on several models, such as European and American models, to predict the mechanical behavior of rubber concrete subjected to fire loading. The thermal parameters such as thermal conductivity, heat capacity, and density are variables as a function of temperature. First, the temperature is computed using the finite difference method (FDM) using the implicit scheme. The mechanical parameters in the literature are computed and plotted, such as compressive strength, tensile strength, peak strain, and stress-strain relationship, and then the mean value is estimated to develop a new probabilistic model at elevated temperatures. To validate the developed model, we compare the behavior of rubber concrete with experimental measurements.