Spin- and angle-resolved photoemission spectroscopy (SARPES) has been applied to the study of spin-polarized electronic structures of face-centered tetragonal (fct) Co thin films with thicknesses from 2 to 9.5 monolayers (MLs). We have clearly observed two dispersive majority and minority spin band structures originating from the bulk-like bands. These observed band structures show narrower width for thinner film due to an in-plane lattice expansion at the Co–Cu interface.