A series of hydrazinated mixed nickel manganese zinc ferrous hydrazine fumarate complexes were synthesized from aqueous mixed metal chloride solutions and sodium fumarate-hydrazine hydrate mixture. The detailed characterization was carried out by chemical analysis, infrared spectroscopy and isothermal mass loss studies. The hydrazine ligand in these complexes shows bidentate bridging nature while fumarate anion exhibit monodentate behavior. These complexes act as single source precursors for nanosize ferrites. Thermal decomposition of these precursors was studied upto 800 degrees C in static air using simultaneous TG/DTA. The thermal decomposition study indicates 3-step decomposition of these precursors into nanosize mixed metal oxides. The nanosize mixed metal oxides were then characterized by X-ray diffraction, transmission electron microscopy and infrared spectral studies. (C) 2013 Elsevier B.V. All rights reserved.