Mo0.1Ce0.9O2+δ (MDC) impregnated nickel-yttria-stabilized zirconia (Ni-YSZ) has been fabricated and evaluated in both solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) modes. The optimal electrode performance has been obtained by MDC modified Ni-YSZ with MDC loading of about 294 mg cm−3 resulted from 7 repeated impregnation cycles. Single cells with the configuration of MDC modified Ni-YSZ as the hydrogen electrode, YSZ as the electrolyte and (La0.75Sr0.25)0.95MnO3–YSZ as the oxygen electrode show a power density of 837 mW cm−2 and a polarization resistance of 0.15 Ω cm2 (under open circuit condition) at 800 °C when using hydrogen as the fuel and ambient air as the oxidant in the SOFC mode. Such cells show current densities of 1.14 A cm−2 and 1.60 A cm−2 with 30 vol.% and 70 vol.% absolute humidity (AH), respectively at 800 °C with an applied voltage of 1.6 V in the SOEC mode. The cells with MDC modified Ni-YSZ as the anode also show very good sulfur tolerance and coking resistance. Power densities of 440 mW cm−2 and 420 mW cm−2 can be obtained when using H2 with 50 ppm H2S and methane as the fuel, respectively under a current density of 0.60 A cm−2 at 750 °C. It has been revealed that MDC enhances the electrical conductivity and improves the triple phase boundary (TPB) length, resulting in significant enhancement of the cell performance when using the MDC modified Ni-YSZ electrode.