Education is centre stage in current UK government initiatives to promote multi-agency team work. This paper draws on a research project which explored the way in which multi-disciplinary teams work and learn together in their practice with children, to consider the implications of "joined-up" practice for theorizing dilemmas of knowledge creation and identity transformation for professionals in multi-agency teams. The paper focuses primarily on the experiences of education professionals. We exemplify some dilemmas of ?joined-up' team participation in specific workplace activities involving knowledge exchange. We then explore the impact of belonging to multi-agency teams on professional roles, identities and learning. The paper then summarizes strategies which professionals used for resolving dilemmas around learning and knowledge creation, and considers how participating in shared workplace activities might enable or constrain professionals to consolidate their professional identities and learning. Drawing on theoretical research into workplace participation and professional learning, the paper examines implications for theorizing the professional identity of teachers in multi-agency team work, within a systemic model that takes account of: creating new knowledge and practice; enhancing professional identity; and building inter-professional communities.