In this research, syndiotactic polystyrene (sPS) based nanocomposites containing 3 wt% of Cu-nanofibers and Ag-nanoparticles were prepared using the melt-mixing technique. TEM and SEM micrographs verified a fine dispersion of the nanoparticles in the polymeric matrix. Tensile testing experiments showed slight improvement of the mechanical properties of the nanocomposites, compared to neat sPS. From the thermogravimetric analysis a substantial enhancement of sPS thermal stability was found, caused by the addition of nanofillers. The temperature corresponding to a mass loss of 0.5% is 295 degrees C for the sPS, 344.5 degrees C for the sPS-Cu and 361.8 degrees C for the sPS Ag nanocomposites. The activation energy of thermal decomposition is 152.5 for sPS, 177.8 for sPS-Cu nanofibers and 198.7 kJ/mol for sPS-Ag nanoparticles. From pyrolysis-gas chromatography mass spectroscopy (Py-GC MS) study of sPS and its nanocomposites, it was found that even though the nanocomposite materials are more stable than sPS, the decomposition mechanism remains the same. Also, the main decomposition products of all materials under study were found to be styrene, its dimmer and trimmers. (C) 2013 Elsevier B.V. All rights reserved.