This article presents a quasi-experimental study into the effects of a course offered to subject matter student teachers that focused on Socratic Dialogue as a way to enhance their interactional scaffolding of advanced second language learning. Within the framework of the sociocultural theory of learning and second language acquisition, the study uses a scoring rubric to capture and quantify the quality of Teacher–Learner Dialogues (TLDs). 202 10-minute TLDs were scored and a multivariate analysis revealed medium to very strong effect sizes. Findings indicate that familiarity with the underlying tenets of Socratic Dialogue, understood as fostering learner agency, was able to affect teachers' ability to provide interactional scaffolding in TLDs with second language learners. At the same time, teachers became more mindful of learner language. The article concludes with recommendations for teacher education.