Cu2O/Ag composite nanospheres (CNSs) with tunable Ag coverage and optical properties have been prepared based on a one-pot room temperature method by adding AgNO3 solution to fresh Cu2O nanosphere-produced mother solution in various ratios. Ag+ ions can be reduced by the primary Cu2O nanospheres in the acidic solution, and the obtained Ag nanoparticles can be deposited on the surfaces of the Cu2O nanospheres. The photocatalytic activity of Cu2O/Ag CNSs has been evaluated for photodegradation of methyl orange (MO) dye under visible-light irradiation, which demonstrates that Cu2O nanospheres with Ag loading exhibit significantly enhanced photocatalytic activity compared with pure Cu2O counterparts, and their photocatalytic properties depend on the coverage density of Ag nanoparticles. The enhanced photocatalytic activity can be attributed to the deposition of Ag acting as electron sinks to prevent the recombination of the photogenerated electrons and holes, and the plasmon resonances of the Ag nanoparticles generating more electronhole pairs in the semiconductor.