Electrospinning of sols obtained through hydrolysis and partial condensation of tetraethoxysilane is a method for preparing silica nanofibers. The effects of the parameters used in the nanofiber fabrication process on the diameter and morphology of the fibers were investigated for controlling the diameter of the resultant fibers. The thinnest smooth fibers (average diameter: 305 nm) were obtained under the following conditions: sol viscosity, 0.14 Pa·s; applied voltage during electrospinning, 25 kV; needle-to-collector distance, 10 cm; and flow rate, 8 mL/h. Decreasing the viscosity of the sol to less than 0.1 Pa·s resulted in the generation of beads and beaded fibers. Thicker fibers were obtained by increasing the viscosity and decreasing the applied voltage during electrospinning. In contrast to the viscosity and applied voltage, the needle-to-collector distance, which was varied in the range 5–15 cm, and the flow rate of the sol (2–11 mL/h) extruded from the needle did not influence the diameter of the fibers significantly.