The aim of this study was to examine the properties of polyester nanofibers produced by the electro-spinning method. Solvent-spun nanofibers with different concentrations of poly(ethylene terephthalate) (13,16, and 20 wt %) were produced. The morphology and surface energy of the fibers were analyzed by scanning electron microscopy and contact angle measurements. Tensile testing, dynamic mechanical analysis, and differential scanning calorimetry were carried out to characterize the thermal and mechanical properties. X-ray diffraction and attenuated total reflection Fourier transform infrared spectroscopy tests were performed to analyze the microstructural properties. The results show that a nanoweb of the 16 wt % solution had better mechanical and thermal behaviors because of the increased molecular orientation in the amorphous structure and the narrower fiber diameter distribution in the web. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 759-769, 2011