The geological storage of carbon dioxide CO2 in deep saline aquifers has been gaining interest to reduce greenhouse gas emissions. Thus, the number of studies focusing on the solubility of CO2 in brines at high temperature and high pressure has been increasing in the last decades, but information remains scarce particularly at high salt molality. In this work, an analytical method was developed for experimental measurement of CO2 solubility in sodium sulfate (Na2SO4) solutions (1 and 2 mol/kg) at high pressures (1.5−20 MPa) and temperatures (303.15, 323.15, 373.15, and 423.15 K). Forty-eight experimental points of CO2 solubility are reported here. Solubility has been shown to increase with pressure evolution and decrease with temperature and Na2SO4 concentrations evolution. A discussion is proposed about the salting-out effect in Na2SO4 solutions, and a comparison is made with the same effect in aqueous systems containing sodium chloride (NaCl) and calcium chloride (CaCl2).