Accelerated aging (30 min at 400 A degrees C) has been shown to alter the mechanical properties of Cu-Nb nanolaminate systems. The Cu-Nb nanolaminates produced were 1,000-nm thick with alternating 20 or 100-nm-thick individual layers, which were fabricated by magnetron sputter deposition. Unaged Cu-Nb systems increased in hardness (from 4.3 to 5.5 GPa) with decreasing layer thickness. After aging, the nanolaminates with 20 nm layers softened greatly (5.5 GPa decreased to as little as 1.3 GPa), yet nanolaminates with 100 nm layers hardened slightly (4.3-4.8 GPa). Both nanolaminate structures exhibited significant residual tensile stress, which was further increased by up to 70 % (100 nm layers) and 120 % (20 nm layers) after accelerated aging. X-ray diffraction showed the presence of primary textures and high stress in niobium layers for unaged systems.