Polymer organic-inorganic hybrid nanofibers constitute a new class of materials in which the polymeric nanofibers are reinforced by uniformly dispersed inorganic particles having at least one dimension in nanometer-scale. In the present study, polyacrylonitrile (PAN) and PAN/Na-montmorillonite (PAN/Na-MMT) nanofibers were conducted via electrospinning process. Electrospun PAN and PAN/Na-MMT fibers with the respective mean fiber diameter of about 220 and 160 nm were prepared. The influence of the clay-montmorillonite on the morphology and diameter of nanofibers was investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM) techniques. The microscopic techniques propose that the PAN/Na-MMT composite nanofibers show lower mean fiber diameter than the neat PAN nanofibers. Besides, the difference in nanoclay-content has a slight effect on the distribution of fibers diameter. Thermogravimetric analysis (TGA) results suggest that introduction of clay-nanomaterials improves the thermal characteristics of fibers.