Ag-Cu alloy nanoclusters have been formed by sequential ion implantation. As the as-implanted sample is annealed in a reducing atmosphere, the optical absorption spectrum displays a new shoul- der peak. Transmission electron microscopy bright-field image, selected area electron diffraction pattern and high-angle annular dark field scanning transmission electron microscopy image analy- ses show that core-shell nanoclusters have been fabricated. The evolution of core-shell nanoclusters at elevated temperature was also studied.