The influence of the support in the steam reforming of phenol at 700 °C has been examined over Ni/K-La-ZrO2 and Ni/Ce-ZrO2. Both catalysts exhibited high activity and good stability in terms of phenol conversion. However, Ni/K-La-ZrO2 showed a pronounced change in product distribution with TOS, which was related to deactivation for the water–gas shift. The high activity observed for the water- gas shift over the unsupported nickel and the difference in the location of coke between the two nickel catalysts are suggested to be the key reasons for the difference in catalyst stability. The red-ox properties of Ce-ZrO2 are proposed to result in more oxygenated species (Osingle bond and OHsingle bond) than the non-red-ox K-La-ZrO2. These oxygenated species, which are suggested to undergo back-spillover from the support to the nickel surface, could be responsible for keeping the nickel surface clean by gasifying the carbonaceous species accumulated on nickel.