Nano-size Ag-N co-doped ZnO/CuO composites have been synthesized and tested for their photo-catalytic activity towards degradation of methyl orange in aqueous solution under visible as well as UV radiations. Crystal structure, surface functional groups, metallic composition and band structure of as-synthesized nano-material were investigated using XRD, FTIR, AAS and UV-Vis spectroscopic techniques, respectively. Ag-N co-doped ZnO/CuO photo-catalyst showed higher photo-catalytic activity than Ag- or N-doped and undoped composite photo-catalysts. The observed highest activity of Ag-N co-doped ZnO/CuO among the studied photo-catalysts, is attributed to the cumulative effects of lowering of band-gap energy and decrease of recombination rate of photo-generated electrons and holes owing to doped N and Ag, respectively. Effects of photo-catalyst load, solution pH and substrate initial concentration on the degradation of methyl orange have also been studied.