The thermal conductivity of three aqueous Na2CO3 solutions of molality (0.4966, 1.0483, and 1.6650) mol.kg(-1) has been measured with a concentric-cylinder (steady-state) technique. Measurements were made at three isobars, (0.1, 10, and 30) MPa. The range of temperatures was (293.15 to 627.06) K. The total uncertainty of thermal conductivity, pressure, temperature, and molality measurements was estimated to be less than 2%, 0.05%, 30 mK, and 0.02%, respectively. The experimental and calculated values of thermal conductivity for pure water from IAPWS formulation show excellent agreement within their experimental uncertainties (AAD within 0.44%) in the temperature range from (308.4 to 704.2) K and at pressures up to 60 MPa. Correlation equations for thermal conductivity of the solutions studied were obtained as a function of temperature, pressure, and composition by a least-squares method from the experimental data. The AAD between measured and calculated values from this correlation equation for the thermal conductivity was (0.5 to 0.7%)