The selective CO oxidation over Pt-Co/Al2O3 catalyst in hydrogen-rich streams was studied in the presence of Ce, Mg, Mn, Ze, and Fe as the second promoters. The catalysts were prepared using incipient to wetness co-impregnation, and tested in a microflow reaction system. The effects of the second promoter were investigated in near 100% CO conversion conditions both in the absence and presence of CO2 and H2O in the feed. 100% CO conversion was obtained with the addition of each second promoter at 110 degrees C while Pt-Co/Al2O3 catalyst had 96%-98% CO conversion. It was also found that changing the Pt ratio from 1.4 wt.% to 0.7 wt.% at 110 degrees C did not have any significant effects on catalysts containing Ce, Mg, or Mn, and it had negative effects in the case of Fe and Zr. The CO conversion decreased for all the catalysts in the presence of 25% CO2 in the feed as expected, and recovered fully or significantly with the addition of 10% H2O. The addition of Ce, Mg, and Mn as the second promoter also improved the performance 2%-3% compared to Pt-Co/Al2O3 catalysts in the presence of CO and H2O. The increase in the reaction temperature to 130 degrees C decreased the CO conversion over all the catalysts.