This study aims to examine how pre-service teachers learn to teach in Australia context during their practicum and how this learning experience constructs their identities as teachers through activity theory framework. Data were drawn from interviews with two pre-service teachers, interviews with their supervising teachers and university mentors, lesson plans, and supervising teacher's feedback. The findings indicate that the two pre-service teachers' identity formation is a continuing process and an outcome of the collective activity through their interaction with their coordinating teachers, mentors and students. We argue that teachers' identity formation is related to their agency to seek and offer support to others. The pre-service teachers could produce and reproduce their identity in the relevant community through their agentive action to interact with others.