The growth of Ag clusters on Si(111)-7×7 surfaces was studied by scanning tunneling microscopy (STM), ultraviolet photoelectron spectroscopy, and x-ray photoelectron spectroscopy (XPS). A shift in the Ag 3d binding energy and a noticeable change in the valence-band structure reveal a significant modification of the electronic states of the Si(111)-7×7 surface and the dispersed Ag clusters, which had a strong dependence on the coverage of Ag. Furthermore, these Ag clusters deposited on the Si surface alter the behavior of oxygen adsorption on the Si(111)-7×7 surface. As evidenced by XPS, the presence of Ag inhibits the adsorbed surface oxygen species, the ins-ins and ad-ins oxygen, in which “ad” denotes an O atom bonding on top of the Si adatom and “ins” denotes an O atom inserted into a Si adatom back bond. The STM and high-resolution electron energy loss spectroscopy results show that the ins-ins oxygen species are more significantly suppressed by the Ag clusters compared to the ad-ins oxygen.