The cross second virial coefficient and the low-density shear viscosity, thermal conductivity, and binary diffusion coefficient of mixtures of water (H2O) with nitrogen (N-2) were obtained at temperatures of up to 2000 K with high accuracy employing statistical thermodynamics and the kinetic theory of polyatomic gases, respectively. The required intermolecular potential energy surface (PES) describing H2O-N-2 interactions is presented in this work, while existing PESs from the literature were used to model H2O-H2O and N-2-N-2 interactions. All of the applied PESs are based on high-level quantum-chemical ab initio calculations. The values predicted for the investigated thermophysical properties agree satisfactorily with the existing experimental data and are probably the most accurate estimates currently available. Practical correlations of the cross second virial coefficient and the low-density binary diffusion coefficient, which are based exclusively on the calculated values, are also provided.