The effects of Ru or Rh addition on the catalytic oxidation of methane over Pt/ZrO2 were investigated at low temperatures under an oxidizing atmosphere. Adding Ru slightly improved the initial activity but significantly suppressed deactivation in the presence of SO2. Deactivation by SO2 was not observed using Ru-Pt/ZrO2 with Ru loadings of 2 wt% or higher. Adding Rh improved the initial activity significantly, but Rh-Pt/ZrO2 catalysts exhibited deactivation in the presence of SO2. Characterization of the catalysts revealed that the loaded Pt is maintained in a high oxidation state, similar to that of Pt4+, in Ru-Pt/ZrO2. These results suggest that the role of Ru is to maintain Pt in a high oxidation state in which Pt exhibits high activity for methane oxidation.