Presently the development of green chemistry in the synthesis of various nanoparticles and nanocomposites with the use of plants and plant extracts has achieved great attention. This study reports the synthesis of ZnO:CuO nanocomposite in an environmental manner using Aloe Barbadansis leaf extract as a capping agent. The chemical co- precipitation method was adopted for the size controlled preparation of the composite. The prepared samples of ZnO:CuO naocomposite was characterized using Energy Dispersive Spectroscopy, Electron Microscopy and X-ray Diffraction. Photocatalytic activity of ZnO:CuO naocomposite was studied on the photocatalytic degradation of methyl orange under UV irradiation. Photocatalytic study of the samples advocates the efficiency of biologically synthesized ZnO:CuO nanocomposite as a good catalyst. [ABSTRACT FROM AUTHOR]