In this work a single valence-tautomeric cobalt complex placed in a dc electric field has been examined. Along with the interaction with the electric field, the model employed accounts for intramolecular transfer of the excess electron as well as vibronic and exchange interactions. To obtain the energy spectrum of the valence-tautomeric complex in the electric field, the vibronic problem of the pseudo-Jahn–Teller effect has been solved. The vibronic (hybrid) wave functions and energy levels were used to calculate the temperature and field dependence of the molecular magnetic moment, as well as the polarization and shape of the absorption band in the near-IR range, which is related to the light-induced transfer of the electron from the catecholate ligand to the metal ion. It is predicted that the application of a dc electric field leads to electric polarization and a significant change in the magnetic and spectroscopic properties. The unique possibility of controlling electrically the magnetic state and optical and polarization characteristics of a valence-tautomeric molecule is predicted.