This article contributes to the development of a thermodynamic model for simulating CO2 solubility in pure water and aqueous brines under different conditions of temperature, pressure and ionic strength. The modeling activity-fugacity (γ-φ) approach allows calculating CO2 solubility, based on the Pitzer electrolyte theory for activity coefficient and Peng-Robinson's equation of state for fugacity. The present work proposes a new set of Pitzer interaction parameters through the set of CO2 solubility data in saline systems such as CO2-H2O-NaCl and CO2-H2O-Na2SO4. The determined model is capable of covering a wide T − P − I range (273.15–473.15 K, 0.1–40 MPa and 0–6 mol/kg). Average absolute deviation of CO2 solubility is about 5% compared to a large number of experimental data available (more than 700 data analyzed). New experimental solubility data for the CO2-H2O-NaCl-Na2SO4 system were also acquired in this study (303.15–423.15 K, 1.5–20 MPa and 0–6 mol/kg) to test the model's capacity: it is able to describe the CO2 solubility in aqueous salt mixtures without any further optimizations of interaction parameters.