How does teachers' target language proficiency correlate with their ability to use the target language effectively in order to provide optimal learning opportunities in the language classroom? Adopting a conversation analysis approach, this study examines the extent to which teachers' use of the target language in the classroom creates learning opportunities for L2 learners. The article also explores the relationship between teachers' target language proficiency and the ways in which they use the target language in the classroom to engage learners in the learning process. Analyses of the lesson extracts show a complex relationship between teachers' general language proficiency and their ability to make use of their proficiency to support student learning in the L2 classroom. The article concludes that while teachers' general proficiency significantly affects the way they use language in the classroom to promote learning, their classroom proficiency is at least as important as their general proficiency. This has implications both for teachers and teacher educators.