Silver has been successfully intercalated underneath a monolayer of graphite (MG) adsorbed on Ni(111) by deposition on the MG/Ni(111) surface at room temperature and subsequent annealing to 350-400 °C. The surface phonon dispersion of the MG/Ag/Ni(111) system has been measured in the direction of the Brillouin zone using high resolution electron energy loss spectroscopy. The dispersion curves were found to be almost identical to those of bulk graphite, which is in contrast to the softened graphite-like phonon modes observed for the MG/Ni(111) system. This suggests that the stiffening of the phonon modes induced by silver intercalation is caused by a weaker interaction of the states of graphite with the substrate. These results demonstrate that a weakly bonded graphite monolayer, whose chemical properties are very similar to those of bulk graphite and which is stable up to 400 °C, can be synthesized in situ on Ni(111) after intercalation of silver.