An attempt has been made in this research for degradation of Reactive Black 5 (RB5) employing catalytic ozonation over the composite catalyst of lanthanum oxide and cobalt oxide (La-Co-O). The catalyst was prepared by co-precipitation method. Synthesized catalyst was characterized by XRD, SEM and BET techniques. The efficiency of catalytic ozonation was compared with ozonation and with adsorption alone. The COD removal efficiency using the La-Co-O catalyst was 68% which is higher than the single ozonation process. The different parameters like the effect of catalyst dose, initial dye concentration, and initial pH of the solution were studied. It was concluded that the degradation efficiency for RB5 was improved by almost three fold in the presence of the catalyst compared to only ozonation.