Electrical discharges generated at water-gas interface in a dielectric barrier discharge reactor has been utilized for the degradation and mineralization of a model aqueous organic pollutant, viz., methyl orange. Mineralization of the dye is identified by an online infrared gas analyzer and confirmed by a total organic carbon analyzer. It has been observed that both degradation efficiency and mineralization of the dye increases on addition of modified alumina catalyst to the plasma reactor. On addition of FeO x/Al2O3 catalyst, the mineralization efficiency increases from 31% with plasma reactor alone to 38%. It has been observed that dye degradation followes first-order kinetics and degree of mineralization increases as a function of time with decreasing energy yield.