Background: A reformed view of science education positions argumentation as a central epistemic discourse practice in the science classroom, however, science education researchers have found that typical norms of classroom discourse fall short of promoting argumentation. Recent scholarship on teachers' personal epistemologies has suggested that epistemic cognition may impact the dialogic practices adopted in the classroom. Purpose: We explored how teachers' epistemic cognition, specifically epistemic aims and epistemic ideals, impacts their dialogic processes as they engage in argument-based inquiry. Sample: Seventy-seven kindergarten through eighth-grade teachers in eight moderate to large school districts in the Midwest United States served as participants in the study. Design and methods: Teachers recorded science lessons in which students were asked to analyse the results of an investigation and engage in evidence-based argumentation to promote meaning making. To investigate teachers' epistemic cognition, participants were interviewed using the Teacher Beliefs Interview. Results: Teachers' reflective epistemic cognition varied according to their orientation to science instruction and this orientation impacted the discursive climate of their classrooms. We found that teachers' epistemic aims and ideals shaped their dialogic feedback practices as well as the quality of their implementation of evidence-based argumentation in the classroom. Conclusion: This study shows that there is a relationship between teachers' epistemic cognition and their use of dialogic feedback to promote evidence-based argumentation in science classes. Further, the type and quality of dialogic feedback vary according to teachers' epistemic cognition; specifically their epistemic aims and ideals. With respect to professional development it may be beneficial to consider helping teachers acquire not only dialogic feedback skills but also a suite of epistemic aims and ideals that align with reformed views of science education.