The purpose of this study is to identify the collaborative reflection process of preservice teachers in the community of practice. Eleven reflection sessions in the Friendship Project were audiotaped. The transcribed data were analyzed using M-GTA, and five categories were generated. The findings are as follows: (1) Preservice teachers shared their knowledge about children and activities in the Friendship Project. (2) They reflected on their educational practices based on their understandings of individual children, groups of children, and children in general. (3) They evaluated the effectiveness of their educational practices by examining their actions and the activities in the Friendship Project. (4) They shared their prospects for future activities by discussing their expectations from children and alternatives to preservice students’ actions and to the activities in the Friendship Project. (5) The supports by others affected the collaborative reflection process. Preservice teachers reflected on their educational practices by comparing them with other teams’ practices and by referencing the opinions of other preservice teachers, university instructors, and children’s parents.