The phase diagram of the Ag-Ni binary system has been evaluated by using the calculation of phase diagrams (CALPHAD) method based on experimental data of the phase equilibria and thermodynamic properties. Gibbs free energies of the liquid and fcc phases were described by the subregular solution model with the Redlich-Kister equation. On the basis of the thermodynamic parameters of the Ag-Ni, Ag-Cu, and Cu-Ni systems, and experimental information of the phase equilibria in the Ag-Cu-Ni system, the thermodynamic assessment in the Ag-Cu-Ni system was carried out. The calculated results in both the Ag-Ni and Ag-Cu-Ni systems are in reasonable agreement with experimental data.