Understanding of the mechanisms behind electrocrystallization in glassy electrolytes has been the subject of permanent research. For lead oxyfluoroborate glasses, evidence exists that this phenomenon involves redox-type electrochemical reactions that develop at the glass–electrode interfaces, promoting β-PbF 2 crystallites nucleation. Here, especially, the form by which these glasses dielectrically act in response to the electric field in the stage preceding crystallization incidence was investigated through applying electrochemical impedance spectroscopy and polarization/depolarization current techniques. This study shows that formation of space-charge regions, which reveal a peculiar dynamics and should incorporate the electroactive species susceptible to redox reactions, is the very first detectable reaction of these glasses during evolution to electrocrystallization.