We synthesized Ag@Ni core-shell nanoparticles by the solvothermal hot injection method and characterized them as for their shape and size by dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). We previously demonstrated their core-shell structure by scanning transmission electron microscopy with energy dispersive spectroscopy (STEM-EDS). The silver/nickel phase diagram was calculated by the CALPHAD method, and the melting points of 10, 15, and 20 nm silver nanoparticles were predicted at 930.2, 940.7, and 946.0 degrees C, respectively. We took advantage of the nickel shell to avoid silver sintering and to confirm the calculated melting point depression (MPD). The results obtained from the differential scanning calorimetry (DSC) experiments revealed the melting points of 11-15 nm nanoparticles at 944-949 degrees C in agreement with calculated values.