The thermal behaviour of p-toluidino-p-chlorophenylglyoxime (pTpCPG) and its Cu(II), NI(TI), and Co(LI) complexes have been studied by DTA and TG. It was found that pyrolytic decomposition undergoes with melting in both Ligand and its metal complexes and metal oxides remained as end products of the metal complexes. The ligand decomposes in two stages through two different mechanisms and the metal chelates undergo decomposition in three stages. GC-MS combined system was used to identify the products during pyrolytic decompositions. The pyrolytic end products were identified by X-ray powder diffraction.