Electrical discharges generated at water–gas interfaces in a nonthermal plasma (NTP) reactor were utilized for the degradation and mineralization of a model aqueous organic pollutant, methylene blue (MB). NTP-based advanced oxidation processes present a huge potential to remove contaminants from wastewater. The degradation of pollutants greatly depends on the active species generated during the NTP process. In this study, on adding catalyst to plasma reactor, both degradation efficiency and mineralization of the pollutants increased. It was also observed that MB degradation followed the first-order kinetics and degree of mineralization increased as a function of time.