Nanoparticles NiFe2 xTbxO4 (x 0.00, 0.04, 0.08, 0.12) ferrite was prepared by solgel combution method. The samples were characterized with X ray diffraction and TEM measurements. The effect of Tb3+ cations substitution on structure of prepared nanoparticles was investigated. From the analysis, the system was found to be inverse spinel cubic structure. The lattice parameter (a) changes increases with Tb doping content. Room temperature DC electrical resistivity decreases. Dielectric properties have been studied in the frequency range of 1 kHz to 5 MHz. Permittivity and tangent loss (tanδ) decreases with the substitution of Tb3+ in parent crystal structure.