This work was to investigate the effects of Ag-based catalysts and the addition of a second metal (Sn or Cu) loaded on an 0.1% wt% Ag catalyst on the ethylene epoxidation performance in a low-temperature and atmospheric pressure parallel plate dielectric barrier discharge (DBD) system with two frosted-glass plates and a separate N2O/C2H4 feed. The combined catalyst-DBD system with the 0.1 wt% Ag catalyst was found to provide significantly higher ethylene oxide (EO) selectivity, as compared to the sole DBD system, due to the additional surface reactions on the boundary area between the Ag active sites and silica support. The addition of the second metal (Sn or Cu) on the 0.1 wt% Ag catalyst substantially improved the EO selectivity, by reducing Ag particle sintering for Sn and increasing in the stability of oxometallacycle intermediates with high activation barriers for the formation of other products, causing an increased selectivity towards EO formation for Cu.