This study examines students' experiences using letter writing designed as a socio-cultural-based tool for critical friend work to promote dialogue and critique of their self-study teacher research projects. It seeks to understand their diverse experiences to inform future practice and contribute to the knowledge base of critical friend work in teacher research. Understanding how, and in what ways, critical friends worked together, listened, and voiced their thinking with peers has applicability to other classrooms and for teacher educators interested in tapping into the potential of peer audience to support teachers' professional development.