Electrical conductivity of mixed calcia/yttria-stabilized zirconia (CYZ) was measured by the complex impedance method in the temperature range from 600 to 1100K and compared with those of yttria-stabilized zirconia (YSZ) and calcia-stabilized zirconia, respectively. Non-linear Arrhenius behavior was observed for all the three samples examined. It was shown that in both high- and low-temperature ranges, the introduction of CaO as the third component into the system ZrO 2 -Y 2 O 3 would result in increases in both the activation energy for conduction, E, and the pre-exponential factor, σ 0 . Using the experimentally determined values of E and σ 0 , it was predicted that the conductivity of CYZ would be higher than that of YSZ when temperature increases above 1350K. This phenomenon can be attributed to the fact that CYZ has a larger σ 0 value mainly due to its higher oxygen vacancies concentration compared with YSZ.