Continuous poly(amide-imide) nanofibers were fabricated using a novel electrospinning method with rotating and re-collecting cylindrical collectors. The nanofilaments were modified using various post-treatments, i.e. glycerol treatment and thermal imidization under tension, for possible application as high-performance reinforcements. Morphological and mechanical properties of continuous poly(amide-imide) nanofibers prepared by the electrospinning process and various post-treatments were measured. Severe adhesion between individual nanofibers within fiber bundles was inhibited through surface treatment of the electrospun nanofiber bundles by spraying with glycerol. The morphological and mechanical properties of the continuous poly(amide-imide) nanofibers and thermal stability were improved using thermal imidization at high temperature under tension. The morphological and mechanical properties of the continuous electrospun nanofibers were improved significantly by post-treatments after electrospinning because uniform and complete thermal imidization occurred through the core region of the nanofibers. (C) 2009 Society of Chemical Industry