Although noble metals were used as dopants, the synthesized composite is an economically and environmentally friendly photocatalyst, based on very low concentrations (Au-1 wt% and Ag-5 wt%) of both metals and its reusability in degradation experiments. The bimetallic photocatalyst was characterized by different techniques. Photocatalytic activity of Ag loaded Au/ZnO was evaluated by irradiating the sample solution under solar light and taking Acid Red 18 (AR 18) as an organic dye. The photocatalytic trials confirmed that the Ag-Au/ZnO composite exhibited improved photocatalytic efficiency compared with Ag-ZnO, Au-ZnO, commercial ZnO, bare ZnO, TiO2-P25 and TiO2 (Aldrich) at pH 11 for the mineralization of Acid Red 18 dye. The effects of operational parameters such as the amount of photocatalyst, dye concentration, initial pH on photomineralization of AR 18 dye have been analyzed. Degradation intermediates were analyzed by GC MS, and a degradation pathway was proposed. A mechanism is proposed for the degradation of AR 18 under solar light. Moreover, the Ag-Au/ZnO sample showed excellent stability after four photodegradation cycling runs. The antifungal activity of the prepared materials was tested against Aspergillus flavus, Aspergillus niger, Penicillin chryogenum, Trigoderrna veride and Fusarium oxysporum and their antibacterial activity was tested against Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, streptococcus pyogenes. All doped ZnOs have moderate to good activity compared with bare ZnO.