The purpose of this study is to investigate a preservice middle school mathematics teacher's noticing of student mathematical thinking within the context of lesson study as a component of a teaching practicum course in a teacher education program. This study also examines how preservice teacher education experiences in the context of lesson study influence the noticing skill of the participant preservice teacher, Lisa. Results indicated that the lesson study process supported teacher noticing of student mathematical thinking as the preservice teacher engaged in planning, teaching, and reflecting on the lessons. It was found that the collaborative and reflective structure of lesson study based on the anticipation of students' thinking and interactions between group members significantly increased the level of noticing. The study also revealed that reading about mathematics subjects and the classroom teacher's feedback proved helpful to develop Lisa's noticing.