In this work, new solubility data of CO2 in aqueous piperazine (Pz) solutions were measured over a temperature range from T = (287.1 to 313.1) K and for amine concentrations from m = (0.10 to 2.00) mol.kg(-1). The CO2 partial pressure was kept within P-CO2 = (0.11 to 525.17) kPa using a vapor-liquid equilibrium (VLE) apparatus based on a static-synthetic method. These experimental data and those found in the literature for the ternary system Pz-CO2-H2O were correlated using a model combining the virial equation of state to calculate the fugacity coefficients with a modified Pitzer's thermodynamic model for the activity coefficients. With the new extended interaction parameters beta(0)(i,j) and beta(1)(i,j) that cover a wide range of temperature, CO2 partial pressure, and amine concentration, the model is able to correlate satisfactorily the available reliable experimental solubility data.