Polyacrylonitrile (PAN) nanofibers were prepared via electrospinning, and the PAN nanofibers were then subjected to alkaline hydrolysis with different treatment times. The alkaline hydrolysis behavior of the PAN nanofibers was investigated with ATR-IR and XPS analyses. The results indicate that the nitrile (C equivalent to N) groups of PAN were converted into amide (CONH2) and carboxylic (COOH) groups. The effect of the alkaline hydrolysis on the cyclization of the PAN nanofibers was then investigated using ATR-IR, DSC, and TGA analyses. The functional groups introduced through the hydrolysis of PAN initiated the cyclization reaction at a faster rate, and thus the exothermic cyclization temperature shifted to a lower temperature. In addition, the extent of the stabilization reaction (EOS) of the hydrolyzed PAN nanofibers was higher than that of the PAN nanofibers. It was conclusively demonstrated that the alkaline hydrolysis was effective in improving the cyclization efficiency of the PAN nanofibers. Published by Elsevier Ltd.