The study reported in this article addresses the question of how professional development can increase teacher noticing of student thinking over time. The data come from five teachers' participation in a two-year professional development intervention that combined lesson study, video clubs, and animation discussions. The analysis focuses on whether and how teachers attended to student thinking during study group discussions and when implementing problem-based lessons that they designed collaboratively. The study applies a mixed methods approach to the examination of transcriptions from the video clubs and the classroom implementation of the lessons. The findings reveal that the teachers restated students' ideas and provided examples of how to inquire into student thinking upon the facilitators' request during the video clubs. There was a statistically significant difference in the teachers' use of students' ideas for generalising and synthesising showing that teachers used higher levels of reasoning in the 14 lessons taught over two consecutive years. The intervention supported growth in the teachers' abilities to reason using students' ideas and to make the lessons' goals explicit.