The ternary complexes of copper (II) with salicylidene-2-aminothiophenol (L) and glycine, alanine, valine and histidene amino acids have been studied in solution and in solid state. The mixed ligand complexes have been isolated and characterized based on elemental analyses, IR, UV-Vis, mass spectra, magnetic moment and thermal analysis (TGA). The isolated complexes were found to have the formula [M (L)(AA)] and the copper has the five coordinated square bipyramidal distorted trigonal bipyramidal (SBPTBP) geometry. The thermal stability of the complexes was studied and the weight losses were correlated with the mass fragmentation pattern. In all cases the amino acid moiety is removed first followed by the Schiff base moiety leaving CuO as the metallic residue. The metallic residue was also confirmed by powder XRD powder diffraction. The kinetics of the thermal decompositions of the complexes was studied and the thermodynamic parameters were reported. (C) 2004 Elsevier B.V. All rights reserved.