The total electrical conductivity of the samples in the ternary system (ZrO2)(1-0.08x-0.12y)-(Y2O3)(0.08x)-(CaO)(0.12y) was measured by a direct current four-probe method in the temperature range 773 to 1673 K. It was found that partial replacement of Y2O3 by CaO in the system ZrO2-Y2O3 may enhance the electrical conductivity at higher temperatures. At lower temperatures, however, doping CaO as the third component into the system ZrO2-Y2O3 depresses the conductivity. The observed mixed dopant effect was then analyzed by considering the combined effect of both parameters appeared in the traditional Arrhenius equation, the activation energy, E, and the preexponential factor, sigma(0), on the temperature-dependence of the measured conductivity.