The reversible galvanic cell was employed to determine the thermodynamic properties of liquid copper‐silver alloys in the range of from 0.1 to 0.8 and temperature from the liquidus to 1330°K. The activities of copper were found to be higher than the values reported by Hultgren et al. on the silver‐rich side, whereas they agree well in the high‐copper side. Values of , obtained by extrapolation of the data of this study to 1400 °K, agree well with those reported in literature. , determined in this study, agree with the calorimetric results within the experimental uncertainty. Small values of confirm the nearly regular behavior of the Cu‐Ag system.