Abstract A model is presented for the bulk photovoltaic effect (BPVE) in ferroelectrics which is due to an asymmetry in the ionization cross‐section for polarized impurities. This asymmetry is related to a quantum‐mechanical interference effect and explains the dependence of the BPVE on frequency and polarization of light, and it gives reasons for a possible sign change of the current, as it is observed, e. g., in BaTiO 3 . Numerical results agree nearly perfectly with experimental data for Fe‐doped LiNbO 3 .