Bis-hydrazine metal iminodiacetates have been synthesized by the aqueous reaction between respective metal nitrate hydrate and aqueous solution containing a mixture of iminodiacetic acid and hydrazine hydrate in an appropriate ratio. The compositions of the complexes were assigned on the basis of chemical analyses, magnetic moments, electronic absorption spectra, infrared spectra, thermal analyses and X-ray powder diffraction and found to be MNH(CH2COO)2(N2H2)2 where M = Co, Ni or Zn. Infrared spectra indicate the presence of both bridging bidentate and monodentate hydrazine moieties and monodentate nature of carboxylate ions. The magnetic moments and electronic absorption spectra suggest a high-spin octahedral geometry of cobalt and nickel complexes. The simultaneous TG-DTA analyses reveal that all these complexes undergo two stage decompositions to give respective metal oxide as the final residue. The X-ray powder diffraction patterns are almost super-imposable indicating the isomorphism among these compounds. The hydrazine mixed metal complexes, [M1/3Co2/3NH(CH2COO)2(N2H4)2] where M = Ni or Zn have been prepared by the similar method adopted for the simple metal complexes by using a mixture of corresponding metal nitrate hydrate and cobalt nitrate hydrate instead of metal nitrate hydrate. The composition of the complexes were determined by analytical, spectral and XRD data. These complexes on thermal degradation yield respective metal cobaltites, the formation of compounds which were confirmed by IR spectra and XRD data.