Two novel tetradentate Schiff bases containing oxime groups and their homodinuclear, homotrinuclear Cu(II) and heterodinuclear Cu(II)-Mn(II) and Cu(II)-Co(II) complexes were synthesized. The Schiff base ligands (H2L1 and H2L2) were prepared by condensing of diethylenetriamine with 2-(biphenyl-4-yl)-N-(4-chlorophenyl)-N'-hydroxy-2-oxoacetimidamide (HL1) and 2-(biphenyl-4-yl)-N'-hydroxy-N-(4-methylphenyl)-2-oxoacetimidamide (HL2). Structure assignments are supported by a combination of FT-IR, elemental analyses, inductively coupled plasma optical emission spectroscopy (ICP-OES), magnetic susceptibility, molar conductivity and thermal analyses studies. The free ligands were also characterized by H-1 and C-13 NMR spectra. Elemental analyses, stoichiometric and spectroscopic data indicated that the metal: ligand ratio is 2:1 for the dinuclear copper(II) complexes and 3:2 for the trinuclear copper(II) complexes. The copper(II) ions are coordinated to the oxime and imine nitrogen atoms. Pyrolytic decomposition occurred in melting the metal complexes and metal oxides were the ultimate products.