Cu2O nanowires have been grown on Cu substrates by electrochemical etching followed with dehydration annealing. The as resulted films show excellent hydrophobic performance without organic surface modification. The contact angles (and slide angles) of the as-resulted Cu2O nanowire films grown on Cu mesh, Cu foam, and Cu foil are 168.3 +/- 0.09 degrees (slide angle 19 degrees), 171.7 +/- 0.28 degrees (slide angle 22 degrees), and 172.8 +/- 0.96 degrees (slide angle 2 degrees), respectively. The Cu2O nanowire films on Cu foil represent the best hydrophobic activity for copper-based surfaces without any organic modification and additives. The special configurations of the Cu2O nanowire films on the Cu substrates and their surface energies both have impacts on the excellent hydrophobic performance. The growth mechanism and the performance-structure relationship of the Cu2O nanowire films are also discussed. This study suggests a low-cost and environment friendly method for the preparation of hydrophobic coating material.