The density, isochoric heat capacity, shear viscosity and thermal conductivity of CO₂ gas in the pressure range of 1-50 atm and 300 K are calculated based on a five-centre potential model obtained from ab initio calculations of the intermolecular potential of a CO₂ dimer. The quantum effects of the intramolecular motion are included in a model by the Monte Carlo (MC) Method. Without using any experimental data, the present model achieves excellent agreements between the calculated thermophysical properties and experimental data for all simulated CO₂ densities except the highest one at 135 kg/m3 (3 mol/L). The contributions of potential to the thermophysical properties of the moderate dense CO₂ gas and their dependence on density are investigated in detail. © 2010 Taylor and Francis.