Monodisperse Ni-Zn ferrite nanoparticles of different compositions have been synthesized using two different routes, such as sonochemical and polyol methods. In both the cases, the process was attempted in a single reaction in the absence of any surfactant and deoxygenated conditions. X-ray diffraction data on the samples confirmed formation of pure ferrite phase with spinel structure, and indicated that the sonochemical method produces highly crystalline particles compared to the polyol process. Transmission electron microscopy images reveal formation of different shapes, such as cubic, spherical, flower-like and amorphous depending on the method and composition of the ferrite. The magnetic properties of the synthesized Ni-Zn ferrite nanoparticles, measured by vibrating sample magnetometer at room temperature, show that the highest magnetization value was obtained for the composition of Ni-0.5 Zn-0.5 Fe2O4 in both the synthesis methods. The results of both the methods were discussed by correlating the structure to the magnetism at nanoscales. (C) 2014 Elsevier B.V. All rights reserved.