We prepared Ni and Pd-modified core-shell nanostructures and then analyzed them by scanning electron microscopy, optical microscopy, X-ray diffraction crystallography, FT-IR and UV-Visible absorption spectroscopy. In addition, their CO oxidation performance was tested by temperature-programmed mass spectrometry. The CO oxidation activity showed an order of Ni- () () () in the first CO oxidation run, and greatly improved activity in the same order in the second run. The (the temperature at 10% CO conversion) corresponds to the CO oxidation rate of molCO . For Ni- (), the was observed at in the first run and at in the second run. For the Pd- (), the was observed at a much lower temperature of in the first CO oxidation run, and at in the second run. The CO oxidation activities of transition metal modified core-shell nanostructures presented herein provide new insights that will be useful in developing catalysts for various environments.