In this manuscript, we provide a general theory for how surface phonons couple to molecular adsorbates. Our theory maps the extended dynamics of a surface’s atomic vibrational motions to a generalized Langevin equation, and by doing so captures these dynamics in a single quantity: the non-Markovian friction. The different frequency components of this friction are the phonon modes of the surface slab weighted by their coupling to the adsorbate degrees of freedom. Using this formalism, we demonstrate that physisorbed species couple primarily to acoustic phonons while chemisorbed species couple to dispersionless local vibrations. We subsequently derive equations for phonon-adjusted reaction rates using transition state theory and demonstrate that these corrections improve agreement with experimental results for CO desorption rates from Pt(111). The atomic vibrations of a solid surface can significantly influence the rates and mechanisms of surface chemical processes ( 1– 4). Unraveling these influences experimentally is difficult, necessitating the development of theoretical tools. In this manuscript, we introduce a theory for the coupling between the nuclear dynamics of surface-bound (adsorbed) molecules and the vibrations of the underlying surface. Our theory projects the collective surface vibrations onto the motion of the adsorbate, and in doing so captures how surface phonons spanning several orders of magnitude in length/energy scale influence adsorbate dynamics.