In this study, we aimed to examine a mathematics teacher's actions related to triggering and considering divergent thoughts on the lessons before, during, and after the lesson study process. The participant was a mathematics teacher who participated in a lesson study design. We focused on his lessons before, during, and after the lesson study. The data were collected from the teacher's lessons and these lessons were videotaped. The transcripts of these video records were analyzed in the context of triggering and considering divergent thoughts. The teacher's actions were interpreted and the evidences were provided from the excerpts of the lessons. Throughout the lesson study, the teacher's actions related to considering students' thinking were improved and also varied. We suppose that this study will be a guide for mathematics teachers and teacher educators on triggering and considering divergent ideas.