Epistemic cognition represents aspects of teachers' thinking focused on issues related to knowledge, which may have particular relevance for classroom assessment practices given that teachers must discern what their students know and then use this information to inform instruction. We present a model of epistemic cognition in teaching with a focus on teachers' classroom assessment practices. We argue that teachers' epistemic cognition is inherently more complex than current models developed for learners. Further, we suggest that teachers' epistemic cognition can be supported through the development of reflexivity as an epistemic virtue and that the 3R-EC framework for reflexivity represents one protocol for engaging in reflexive practice that targets epistemic cognition. We close the article with implications for teacher development and with recommendations for further theory and research.