Abstract <p>The series of Sm³⁺ substituted nickel copper ferrites, Ni_0.5Cu_0.5Sm_<i>x</i>Fe_2–<i>x</i>O₄ with (<i>x</i> = 0.1, 0.2, and 0.3), was synthesized by standard double sintered ceramic technique. The phase analysis was characterized by X-ray diffraction studies, which confirmed the creation of single phase. Crystallite size was calculated by using Debye Scherer formula for high intensity peak and found to be in the range from 71 to 90 nm. Surface morphology was studied using a scanning electron microscope and no cluster was observed. The elemental composition of synthesized samples was verified by using energy dispersive spectroscopy and no other elements were detected in the ferrites. Owing to interatomic vibrations in tetrahedral and octahedral sites of present samples two absorption bands were formed which were detected from the spectrum produced by means of Fourier transform infrared spectroscopy. Conductivity of Sm substituted nickel copper ferrites was determined by studying the variation of DC resistivity of ferrites with the temperature. Maxwell–Wagner interfacial polarization in present samples was detected through the use of dielectric spectroscopy and declined when the applied frequency was raised. Dielectric characteristics such as change in dielectric constant, dielectric loss, and AC conductivity versus frequency were studied.</p>