Conceptualizing lesson study as an encounter at the boundaries of research and practice, this study examined teacher-academic collaboration for its potential to shape teacher research identity. We report here a case study of a school where the teachers have been able to present their lesson study works in conferences. Documents produced by the teachers and their academic collaborators from a three-year project served as data sources. Through the lens of boundary crossing, we were able to discern four mechanisms in the collaboration that allowed teachers to cross the boundaries of their field and participate in research practices: problematizing instruction based on evidence from practice; using a research-informed framework for designing and making decisions about the lessons; documenting processes and evidence; and sharing lesson studies. The study contributes to the ongoing work of theorizing lesson study and teacher professional identity.