Ni1-xZnxFe2O4 (x = 0 - 0.8) ferrite nanoparticles were prepared by co-precipitation method annealed in air at 1100°C for 5h. The samples annealed at 1100°C crystallize solely in spinel structure according to XRD measurements of which the lattice constant increased with increasing Zn content. The average particle sizes are in submicron range as revealed by SEM measurements. Magnetization curves were studied by vibrating sample magnetometer (VSM) in the temperature from 80 K to above magnetic ordering temperature from that spontaneuos magnetization Ms and Curie temperature Tc of the samples were determined. Blocking temperature TB was determined by zero-field-cooled (FC) and field-cooled (FC) measurements which showed that the particles are superparamagnetic at temperatures above room temperature and TB decreases with increasing Zn content. Magnetic properties of the samples were compared with those of the bulks and are discussed based on the cation distribution and the concentration of zinc ions in the crystal lattice.