Pure polyacrylonitrile (PAN) nanofibers and functionalized-single walled carbon nanotube (FSWNT), reinforced by PAN nanofibers with variable FSWNT content (up to 1 wt%), were fabricated by electrospinning process. The chemical structure, morphology and microstructure of the electrospun nanofibers have been characterized using Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). SEM analysis of the nanofibers revealed that the deformation of the nanofibers increased with increasing FSWNT concentration. Very smooth surfaces of the composite electrospun nanofibers even for nanofibers with concentration of 1 wt% FSWNT have been successfully prepared because of the high stability dispersion of FSWNTs. Moreover, with increasing the concentration of FSWNT in the PAN solution from 0 to 1 wt%, the average nanofibers diameter increased from 405 ± 54 nm to 488 ± 50 nm. The recorded spectra from FTIR were close to PAN nanofibers with peaks at 2243 cm^-1 (CN stretch), 2932 cm^-1 (CH₂ stretch), 1450 cm^-1 (CH bend) and 1730 cm^-1 (C=O stretch) wavenumbers. FTIR Spectroscopy and XRD studies showed that PAN/FSWNT nanofibers exhibited higher crystallinity compared to PAN nanofibers without FSWNT. The analysis of the microstructural properties of the composite nanofibers with 1wt% FSWNT revealed that they exhibit an enhanced crystallinity from 44% to 48%, and the crystallite size was decreased from 25.0 nm to 19.9 nm, as compared to pure PAN nanofibers. The results indicated that the embedded FSWNTs in the PAN nanofibers nucleated the growth of crystals.