"The purpose of this study was to investigate the experiences and changes of the participants in a physical education T-Mentoring Project. The participants were 4 mentor teachers, 4 mentee teachers, one doctoral students, and one university professor. The mentee teachers experienced team building activities from the November of 2008 through the October of 2009. Their perceptions of experiencing reflective teaching practices and extending pedagogical content knowledge (PCK) were investigated. Experiencing team building activity was comprised of knowing the objectives of team building activities, recognizing the necessity of readiness for the team building activities, experiencing success, experiencing different lesson activities, and executing the different strategies. In experiencing reflective teaching practices, the concepts of ‘instant activity', 'developmentally appropriate activities', 'motivating to participate in physical activity,' 'teaching protocols of lessons', 'keep it brief', and 'using available space appropriately' were well delivered to the mentees. In expanding teaching expertise, 'setting up specific lesson objectives', 'using learning cues', 'providing as many feedbacks as possible', ‘using intratask variation', providing creative learning environments', and 'knowing how to modify games' were improved. They were also encouraged to apply these concepts into their teaching practices. Their extended PCK began to allow their students to learn the lesson contents more and move more vigorously. ※ Key words : T-Mentoring, team building activity, PCK, reflective teaching"