Fe/Cu nanometer-scale multilayers with nominal modulation wavelengths ranging from 5 to 40 nm are deposited by direct current magnetron sputtering on Si (100) substrates. Modulation structures of the multilayers are examined by small angle / wide angle x-ray diffraction (SA/WAXRD) and cross-sectional transmission electron microscopy (XTEM). Hardness of the multilayers is measured by using nanoindentation. All the multilayers have Fe (110) and Cu (111) textures. Interface coherency is observed in the multilayers with designed modulation wavelengths of 5 and 10 nm. The hardness increases firstly and then deceases with increasing the modulation wavelength, and reaches peak value of 7.29±0.29 GPa in the multilayers with nominal modulation wavelength of 10 nm. The evolution of the hardness of the mulitlayers is explained by interface width and modulus difference between sublayers.