Three-dimensionally (3D) hierarchical micro/nano oriented arrays constructed from nanometer-sized building blocks represent an important group of materials and have received enormous attention for a series of applications because they can offer both the advantages of nanosized building blocks and micro- or submicrometer-sized ordered arrays. In this work, 3D flower-like superhydrophilic CuO micro/nanostructures decorated by Ag nanoparticles were synthesized via an amino acid-assisted biomimetic hydrothermal method. Experiments reveal that the product demonstrates excellent sunlight self-cleaning performance in terms of wettability (without the help of high-free-energy compounds and in the absence of UV irradiation) and enhanced photocatalytic activities, which portends a bright future for this material as self-cleaning photovoltaic coatings. It is also a good example for the organic combination of green chemistry and functional materials.