This study examined the impact on 16 middle-school teachers' conceptions of mathematics learning and teaching of reflections on their learning experiences within mathematics professional development. The research questions were: In their reflections, what do teachers express about how they best learned mathematics through these learning experiences? How do teachers extend these ideas to possible modifications of their teaching practice? Data included the teachers' written reflections and field notes, which were analysed using grounded theory. In their reflections, the teachers noted several supportive processes that aligned with recommendations of teaching for mathematical understanding and that they planned to implement in their classrooms. Teachers' reflections were more aligned with teaching for understanding when they thought about their mathematical learning experiences in the role of a learner before considering implications for their teaching. (Contains 2 tables.)