The atomic mean-square displacement (MSD) of granular tin was studied by the Mössbauer effect. Tin grains with a 45-Å average size embedded in an oxide matrix were produced by evaporating the metal in the presence of O2. The lattice parameters and grain-size distribution were measured by electron microscopy. From the temperature variation of the MSD of the granular material, it was found that the <ω−2> moment of the phonon spectrum increases by (8±3)% with respect to the bulk. These results, combined with data of the hyperfine constants and electron microscopy suggest a quasi-isolated grain whose frequency and electronic structure are barely altered and whose interaction with the surrounding oxide is negligible.