This article examines how four second language (L2) teachers' discursive practices changed as they attempted to implement dynamic assessment (DA) in their classrooms. Classroom artifacts, lesson recordings, and reflections from two pre-service teachers and two in-service teachers, both before and after a professional development series on DA, were included in the analysis. Findings revealed that all teachers' approaches to mediation changed. In Pre-DA lessons, teachers defaulted to recasts when attempting to provide mediation. Following the DA professional development series, all teachers expanded the discursive space by providing more prompts and fewer recasts. However, findings illustrated that the four teachers appropriated DA to varying degrees, suggesting that some may have required additional mediation to appropriate all of the distinguishing features of DA. We discuss implications of these findings for teacher preparation.