Complete sets of neutron nuclear data, including all kinds of cross sections, angular distributions of elastic scattering, energy spectra and/or double-differential cross sections of all emitted particles, and gamma production data (production cross sections and multiplicity, angular distributions, and energy spectra) in all kinds of reactions for n + 63Cu and n + 65Cu below 20 MeV are calculated and evaluated. The calculated or evaluated cross sections are in good accordance with the experimental values for those reactions with experimental data. Particularly for the neutron leakage current in the benchmark Oktavian and the effective multiplication factors in six benchmark assemblies, our calculated values are in much better agreement with experimental data than those of several existing evaluation files.