X-ray absorption spectroscopy (XAS) of a plastocyanin from a fern, Dryopteris crassirhizoma (DPc) was studied. The XAS of reduced (CuDPc)-D-I demonstrated the retention of the four coordinated structure at pH 5.0. The EXAFS analyses of the reduced DPc demonstrated that the Cu-axial S-Met95 ligand distance is much shorter than that in the oxidized form. This is the first report for the XAS and EXAFS of an unusual fern plastocyanin