Cubic spinel ferrites are one of the most sought after materials, which have attracted interest in many fields. They are the subject of extensive research owing to their wide range of applications in areas like hyperthermia, information storage systems, gas sensors, microwave devices, magnetic recording media, humidity sensors, etc. Magnesium ferrite, zinc ferrite and the solid solutions between these two ferrites crystallize into cubic spinel structure and have several important technological applications. In this study synthesis of soft magnetic spinel Mg- Zn ferrite(MgxZn1-x Fe2O4, where x= 0.2, 0.4, 0.6, and 0.8) nanoparticles was carried out using the precursor method. Structural and magnetic properties have been studied in detail. XRD data revealed that the structure of these nanoparticles is spinel and crystallite size are in the range 20-44 nm. Lattice parameter decreases with increasing Mg concentration due to the smaller ionic radius of the Mg2+ ion. FTIR spectroscopy also confirmed the formation of spinel ferrite by showing the characteristic absorption bands in the range of 405–396 cm-1 and 566– 555 cm-1. The magnetization showed an increasing trend with increasing Mg concentration up to x =0.6, due to the rearrangement of cations at tetrahedral and octahedral sites, while the coercivity remained small. It is observed that both structural as well as magnetic properties of Mg-Zn ferrite nanoparticles strongly depend upon Mg2+ concentration.