The Ag–Au–Bi system has been thermodynamically assessed through the Calphad approach by combining recently derived experimental data, in particular the phase diagram equilibria and the integral enthalpies of mixing of its liquid phase. A good agreement is obtained between the calculation and the experimental data. The resulting assessment will be incorporated into the thermodynamic description of the quaternary Ag–Au–Bi–Sb system, which is of interest in the lead-free soldering process for electronic materials.