The additive voltage application provides silver nanowires in silver-doped glass prepared by electric field-as-sisted solid-state ion exchange. We experimentally investigate the growth behavior of silver nanowires in a glass substrate. It was found that silver nucleation was initiated at the silver-doped surface contacted with the cathode, and the precipitates dendritically developed toward the doped/un-doped interface as the time of voltage application was increased. After the precipitates reached the interface, the growth direction changed and extended along the interface. Transmission electron microscopy (TEM) observation suggested that the precipitation did not arise from the aggregation or growth of nanoparticles formed in the silver doping process. The experimental results, where the precipitation occurred just below the contacted cathode and was independent of cathode material, indicated that the precipitation resulted from the electrochemical interaction between doped silver ions and supplied electrons. From these findings, we are able to control the silver nucleation area by the arrangement of the cathode configuration.