Nanosized nickel zinc ferrite powders with general formula Ni_1−xZn_xFe₂O₄ (x=0.0, 0.3, 0.5, 0.7, 1.0) were synthesized by an auto-combustion method starting from metal nitrates. X-ray analysis indicated the formation of well crystallized Ni–Zn ferrite phases, and Raman spectroscopy enabled a precise phases identification. The change of the grain size and density with increasing Zn content was confirmed by scanning electron microscopy. Magnetization of saturation and remnant magnetization, both, continuously increase up to x=0.3 of Zn, and then decrease for more Zn. The influence of the grain size of investigated systems on the saturation magnetization was studied. Impedance spectroscopy measurements were carried out in order to investigate the electrical resistivity of materials, showing that grain boundaries have greater impact on total resistivity that grains.