Partial and integral enthalpies of mixing of liquid Ag–Ni and Ag–Ni–Sn alloys were determined at different temperatures, i.e., at 1500 °C for binary Ag–Ni alloys and at 1000, 1220, and 1400 °C for ternary Ag–Ni–Sn alloys. Two different Calvet-type micro-calorimeters were used for the measurements employing drop calorimetry techniques. The binary data were evaluated by means of a standard Redlich–Kister polynomial fit whereas ternary data were fitted on the basis of an extended Redlich–Kister–Muggianu model for substitutional solutions. No significant temperature dependence could be detected for the ternary enthalpies of mixing. From the experimental ternary data, it was possible to deduce the liquidus isotherm at 1000 °C as well as the extension of the liquid miscibility gap at 1220 and 1400 °C.