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This research aimed to study the challenges which elementary teachers deal with lesson study. This research studied challenges in three stages, before, during and after lesson study. To achieve the aim of the research, a case study in a school was used. Participants of this research have been 20 elementary teacher of that school. Data collection tools have been semi-structured interviews with teachers and participatory observation. Coding and categorizing were used to analyzing data. Findings showed that teachers faced with three categories of challenges before lesson study: teachers' knowledge about lesson study, teachers’ motivation to participatet in lesson study, creating group and determination of the responsibilities of the group members. During lesson study teachers faced with three categories of challenges: selecting problem, implementing lesson and data collection, reviewing and criticizing the lesson. After lesson study teachers confronted with three categories of challenges: refereeing, publishing and the lesson study festival.