This paper examines Spanish ‘a pesar de’ from a diachronic perspective. The evolution of this concessive connective is analyzed as a grammaticization process whereby a nominal construction evolves into a connective. In that sense, it supports the view of grammaticization as the evolution of collocations into single units. Throughout its development, automation as a single unit advances together with syntactic generalization (from human adnominals to entire propositions) and semantic generalization (from the notion of sorrow to a more encompassing notion of opposition and then to contradiction). The role of metonymy in this process is also explored. In addition, frequency is proven a crucial factor in grammaticization.