Utilization of PbZrxTi1-xO3 (PZT) nanofibers as functional flexible fillers in sensing and energy harvesting applications requires uniform, submicrometer fibers with a large aspect ratio. Previous studies concentrated on the rheological effects on the fiber's diameter and morphology. However, reports on the effect of electric field on these fiber properties are still scarce. In this paper, the effects of surface charge and electric field on the fiber branching are decoupled. We show unequivocally that the external electric field governs this phenomenon. Low viscosity (∼0.12 Pa s) PZT sols yielded a sharp step-like transition from a large to a small diameter regime at electric fields above 0.8 kV/cm. On the other hand, high viscosity sols (∼0.74 Pa s) yielded a transition from a single to a bimodal distribution at the same electric field, due to the branching effect. An ability to obtain a single or bimodal diameter distribution in the range of 100-800 nm was demonstrated.