Personal epistemological beliefs play a key role in teacher engagement with professional learning, so consideration of epistemic cognition is integral to the designing of sustainable professional learning. This qualitative study uses Chinn et al's (2014) model of epistemic aims, epistemic ideals and reliable epistemic processes (the AIR model) as a theoretical scaffold from which to understand how teachers' ontological and epistemic cognitions affect their engagement with a professional development focused on mathematics anxiety and metacognitive questioning. To cater for the complex situated nature of epistemic cognition, semi-structured interviews were conducted throughout the programme of teacher learning. Thematic analysis identified common influencers on teacher professional learning whilst highlighting conflicts between conceptions of the nature of mathematics and what they had been taught about mathematics teaching. Findings indicate that teachers engaged most fully with situated, practical learning experiences in collaborative learning spaces as they allowed for greater alignment between professional learning content and personal epistemic beliefs. Recommendations for future professional learning and adaptations to the study's epistemic research methodology are provided in the light of the findings.