The screening efficiency of a metal−ferroelectric interface plays a critical role in determining the polarization stability and hence the functional properties of ferroelectric thin films. Imperfect screening leads to strong depolarization fields that reduce the spontaneous polarization or drive the formation of ferroelectric domains. We demonstrate that by modifying the screening at the metal−ferroelectric interface through insertion of ultrathin dielectric spacers, the strength of the depolarization field can be tuned and thus used to control the formation of nanoscale domains. Using piezoresponse force microscopy, we follow the evolution of the domain configurations as well as polarization stability as a function of depolarization field strength.