The purpose of this study was to investigate the changes of one classroom teacher through the consulting of the fourth graders\' tactical game activity. A beginning female elementary school teacher from one metropolitan area was selected as the consultee of this study. She had been consulted about teaching the fourth graders\' tactical game activity unit three times. Participant observations, in-depth interviews, and document analysis were used for the data collection. The data included video files, audio taped files of the interviews, observation checklists, and lesson plans. The data were analyzed through the processes of “organizing data”, “careful reading of the data”, “developing category”, “relocation of categorized data”, “developing categorization system”, and “writing the lists of categorization.” To achieve the trustworthiness of the data, prolonged and consistent observations, triangulation, peer debriefing, negative analysis, and member checks were used. The changes of the consultee were as follows. First, the consultee began to have more positive attitudes toward tactical game activity consulting. Second, the consultee had not only improved her ability in designing and implementing the lesson plans but also had become a better assessor in reflecting her own teaching, which, in turn, enhanced her confidence in teaching. Key words: tactical game activity, consulting, lesson plan design & implementation