The electrical conductivity of electrochemically reduced samples of stabilized zirconia has been measured by impedance spectroscopy, in the range 500–1000 K. Two different conduction processes are involved depending on the deviation from stoichiometry. For small deviations from stoichiometry, the total electrical conductivity increases only slightly. On the other hand, a large increase in the electrical conductivity is observed when the departure from stoichiometry is high. This is interpreted in terms of an increase in the ionic conductivity due to a variation of the dielectric constant and a high electronic conductivity for large deviations from stoichiometry. The variation of this electronic conductivity is more complex than observed in ceria‐based materials.