The comprehensive study of the Ni0.5Zn0.5Fe2O4 ferrite nanopowder crystallized in the inverse spinel structure and synthesized by co-precipitation method is presented. The distribution of Fe3+ cations among tetrahedral and octahedral sites was confirmed. The microstructural investigations revealed the presence of ultrafine grained structure with an average crystallites size in the range of 14 ÷ 20 nm. Raman and Fourier-Transform Infrared (FTIR) spectroscopy studies confirmed typical spinel structure with tetrahedrally and octahedrally iron occupancy as well as indicate co-associated iron-oxide phases considered as factors responsible for the structural disorder. The magnetic properties revealed the superparamagnetic behavior at the room temperature with estimated critical size of single domain particles about 63 nm. The analysis of saturation magnetization pointed to the spin canting phenomenon in the surface layer. The valuation of exchange coupling parameters based on the mean field theory calculation strengthened the conclusion about opposite magnetization arrangement between tetrahedral and octahedral magnetic sublattices.