Centimeter long aluminum-doped zinc oxide (AZO) nanofibers were prepared by electrospinning from polyvinyl alcohol (PVA) aqueous solutions, and the fibers with controlled morphology were expected to have potential applications in gas-sensing and optoelectronic devices. In our research, the diameter and morphology of the nanofibers can be controlled by the applied voltage, the concentration of PVA, and the aluminum (Al) dopant. The introduction of Al resulted in a decrease of the zinc oxide lattice constant by 0.41% and uniform distribution of the nanofiber diameters. Possible mechanisms were proposed to discuss the variations of diameter and morphology.