Experimental measurements were made to assess the electrical conductivity as a function of temperature and NdF₃ concentration (0–20 mol %) of molten systems of (LiF–CaF₂)_eut–NdF₃, (LiF–NaF)_eut–NdF₃, (NaF–CaF₂)_eut–NdF₃ and (LiF–MgF₂)_eut–NdF₃. The experiment used an altering current impedance spectroscopy technique with a platinum–rhodium electrode positioned in a pyrolytic BN tube and graphite a crucible/counter electrode. The conductivity of all systems under study increased with rising temperatures and decreasing NdF₃ concentrations. The Arrhenius equation and linear regression have both been used to describe the experimental data. The results of the ionic conductivity for the temperature 850 °C and NdF₃ concentrations 0, 10 and 15 mol %, respectively, can be compared as follows: the conductivity of the molten system of (LiF–CaF₂)_eut–NdF₃ was determined to be 6.10, 5.95 and 5.10 S.cm⁻¹, the results for the system (LiF–NaF)_eut–NdF₃ were 6.16, 5.56 and 4.13 S.cm⁻¹, the results for the system (NaF–CaF₂)_eut–NdF₃ were 3.78, 3.56 and 2.32 S.cm⁻¹, and finally, the results for the system (LiF–MgF₂)_eut–NdF₃ were determined to be for the same temperature as 5.35, 4.79 and 4.14 S.cm⁻¹, respectively.