This article provides an overview of diachronic and acquisitional grammaticalization and applies it to second language data. Specifically, it argues that the process of acquisition of perfective and imperfective morphology in Catalan as a second language presents parallels with the diachronic grammaticalization process, since in both cases new forms arise in specific lexical and discursive contexts. The results from an analysis of narrative data from learners of Catalan provide evidence for the role of aspectual and discursive characteristics in the development of past morphology and for the bundling of prototypical characteristics (e.g., telicity, foreground, and perfective morphology). These results are analyzed in light of grammaticalization theory, and it is argued that lexical and discursive factors contribute to the noticing of new forms in the input.