We studied the size dependence of the electronic structure of nanocrystalline copper embedded in silicon carbide by means of soft X-ray absorption spectroscopy. Changes in the local electronic states of copper nanoclusters, including the shift in binding energy and the reduction of s–p–d hybridization, occurred. The experimental result was compared with the ab initio self-consistent, real-space, multiple-scattering calculation. The calculation was in good agreement with the trend found in our experimental results. We concluded that the reduction of d–d interaction and the concomitant changes in s–p–d hybridization in copper nanoclusters arise due to the surface effect.