In this work, the degradation of methyl orange (MO) was analyzed by direct light with visible radiation (λ > 450 nm) of a dye solution in the presence of silicon nanowires (SiNWs) or silicon nanowires with copper nanoparticles (SiNWs-CuNPs). The SiNWs were synthesized by metal assisted etching from monocrystalline silicon wafers in aqueous HF / AgNO3 solution, and the CuNPs were deposited on the SiNWs via electroless. Discoloration with visible irradiation of aqueous methyl orange solution (C14H14N3NaOS) in the presence of SiNWs showed an efficiency of 71% after 120 min of illumination. The deposition of copper nanoparticles on the nanowires improves the efficiency of the photocatalytic reaction achieving 89% discoloration after 120 min exposure to visible light. The MO photocatalytic degradation with visible radiation in aqueous solution shows to be efficient in discoloration reaching up to 92% in a time of 150 min in the presence of SiNWs-CuNPs.