Molecular dynamics simulations were performed in order to obtain thermophysical properties of the solid solution of (Np_xPu_1-x)O₂ MOX for the concentrations x = 0.0, 0.2, 0.5, 0.8 and 1.0. Lattice parameter, linear thermal expansion coefficient, enthalpy increment and specific heat at constant pressure were evaluated in the temperature range from 300 K to 3400 K using the NPT ensemble. Elastic constants C₁₁, C₁₂ and C₄₄ were obtained at T = 0 K whereas the bulk modulus was studied in the whole temperature range from 0 K to 3400 K. It was found that most of the evaluated magnitudes closely follow a Vegard's-like law for temperatures below 2000 K. At that point the superionic transition was observed. The results obtained in this work show a good agreement with the available reference data.