Abstract: For the lack of data on the elastic and thermal properties of the orthorhombic LaFeO₃, LaMnO₃ and LaCrO₃ perovskite materials, several elastic parameters including elastic constants, bulk/shear/Young’s moduli, Vickers hardness, Poisson ratio, and shear anisotropy were predicted using the density functional theory calculations. Subsequently, the thermodynamic properties under high temperatures and high pressures conditions were investigated through the quasi-harmonic Debye model. It was found that all three materials are more ionic than covalent, showing ductile behaviors and good thermal shock resistance. Significant differences in the fundamental thermodynamic properties were found. It was mainly influenced by the interactions between different cations and anions. Furthermore, the underlying mechanism affecting the thermodynamic properties were discussed.