Selective hydrogenation of acetylene in rich ethylene was investigated over uncalcined, air plasma, and H-2 plasma Pd/TiO2 and Pd-Ag/TiO2 catalysts. Air and H-2 plasma treatments have different modifying effects on Pd/TiO2 catalyst for selective hydrogenation of acetylene to ethylene. With additional Ag loadings, 1% and 3%, on Pd/TiO2, plasma treatments shift the temperature of maximum C2H4 yield to lower temperatures as compared to Ag shifting the maximum yield temperature to higher temperatures. Air plasma treatment alone on Pd/TiO2 produces the highest maximum C2H4 yield at the lowest temperature among all catalysts tested. H-2 plasma, on the other hand, is more effective in enhancing the performance of the Pd-1%Ag/TiO2 catalyst. Both air and H-2 plasmas show the capability to shift the maximum yield temperatures of Pd/TiO2 and Pd-Ag/TiO2 catalysts to lower temperatures. It provides a new avenue to fine-tune the catalytic reactivity of supported Pd catalysts with or without the Ag promoter to selectively convert acetylene to ethylene in excess of ethylene to meet various industrial demands.