The reaction mechanism of the gold(I)-phosphine-catalyzed addition of phenols to olefins was analyzed by means of theoretical methods combined with polarizable continuum models. Several mechanistic pathways for the reaction were considered and evaluated. The most favorable one includes the ligand substitution of triflate by the alkene in the catalytically active R 3PAuOTf species and subsequent nucleophile attack of phenol on the activated double bond concomitantly with the proton transfer from the OH group to the other carbon atom. The energy barrier for this concerted transition state diminishes dramatically when a proton transfer agent is present. These species are acting as proton shuttles in the proton transfer step. Noteworthy, the proton transfer in the phenol addition, both for the PhOH-or H 2O-assisted processes, is a concerted step. © 2010 American Chemical Society.