The search for polymeric fibers with diameters in the scale of nanometers has been the great objective of researchers and industry, since these fibers have many applications. They can be produced by an electrospinning process from a polymeric solution. In this work, nanocomposites' fibers of polyamide 66 and montmorillonite clay were obtained by melt mixing, following by electrospinning of the solution. Nanocomposites with three different clay concentrations, 2, 3 and 4 wt.%, were obtained by melt mixing, and solutions of these nanocomposites in formic acid were prepared at different concentrations. The influence of the clay addition, nanocomposites' solution concentration, variation of the applied electric field on the mixture and solutions properties and on the average diameter of the nanofibers was studied. Wide-angle X-ray (WAXD) and transmission electron microscopy (TEM) measurements showed that the process of electrospinning was efficient in the maintenance of the clay exfoliation in the fibers. Results of scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) showed that the fibers had average diameters of the order of nanometers, were cylindrical and not porous, having low degree of crystallinity and residual solvent. The addition of clay increased slightly the viscosity of the polymeric solution, which increased the nanofibers average diameter. It was also observed that the increase in the fiber diameters was proportional to the increase of the polymer concentration in the solution. Regarding the applied electric field, it was observed a tendency to reduction in the average diameter of the fibers with the reduction of this parameter.