Nanocrystalline nickel ferrite powder was obtained using high energy reactive ball milling technique. Nickel oxide (NiO) and iron oxide (Fe2O3) powders were used as starting material. Milling was performed in air atmosphere using a planetary ball mill. Milling time was up to 30 hours. The product of milling was annealed at 350 oC for 4 hours in order to eliminate the internal stresses and finish the solid state reaction. X-ray diffraction analysis was used to study the nickel ferrite formation. A nanocrystallite mean size of 10 nm was found after 24 hours of milling. Using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDX) the particle morphology and the chemical homogeneity were studied. It was found that the obtained product has particle size in range of micron and submicron.