This study examines changes in teachers' thinking as they participated in a video club designed to help them learn to notice and interpret students' mathematical thinking. First, we investigate changes in teachers' talk about classroom video segments before and after participation in the video club. Second, we identify three paths along which teachers learned to notice students' mathematical thinking in this context: Direct, Cyclical, and Incremental. Finally, we explore ways the video club context influenced teacher learning. Understanding different forms of teacher learning provides insight for research on teacher cognition and may inform the design of video-based professional development.