Raman spectroscopy investigations of nanofibers of polystyrene loaded with various amounts of multiwalled carbon nanotubes are reported. The modifications of the main Raman bands (D and G) of multiwalled carbon nanotubes due to their dispersion in polystyrene demonstrates and quantifies the stress transfer from the polymeric nanofiber matrix (polystyrene) to multiwalled carbon nanotubes. TGA data show an increase of the thermal stability of polystyrene nanofibers upon the loading with multiwalled carbon nanotubes, conforming Raman data. Published by Elsevier B.V.