The effect of oxidizing agents on mercury oxidation and retention in a laboratory-scale selective catalytic reduction (SCR) system, using a commercial honeycomb vanadia-titania catalyst, is reported in this paper. Two oxidizing agents (HCl and H2SO4) are introduced into the feed gas, individually and in various combinations, at different temperatures and space velocities. The effect of these oxidizing agents on mercury oxidation, in the presence of individual flue gas constituents, is shown in detail. As the concentration of the individual oxidants increases in the simulated flue gas, the oxidation of mercury increases. At high concentrations of 35 ppm of HCl and 50 ppm of H2SO4, respectively, a maximum of 70% of the mercury is oxidized. Temperature is shown to have a positive effect on the extent of oxidation, as does the residence time.