Mixing enthalpies of melts of the binary systems Al-Eu at 1300–1473 K (in the concentration ranges 0 < x Eu < 0.2 and 0.57 < x Eu < 1) and Eu-Sn at 1250–1300 K (0 < x Sn < 0.2; 0.51 < x Sn < 1) were studied for the first time by the isoperibolic calorimetry technique. It was determined that there are moderate (ΔHmin = −23 kJ/mol at x Eu = 0.39) and large (ΔHmin = − 63 kJ/mol at x Sn = 0.42) exothermic formation effects for these melts, correspondingly. Using the information obtained by us and taken from literature, thermodynamic properties of these melts were calculated in the wide temperature range by the model of ideal associated solutions (IAS). The mixing enthalpies of melts of the ternary Al-Eu-Sn system were modeled using the analogous data for the binary boundary systems.