Research in physical education often focuses on how to improve the education of teachers and the achievement of students, based on an assumption of a relatively stable teacher identity. The focus of this study is to unsettle this perspective, drawing on complexity thinking and the concept of becoming to reconceptualize teacher identity as a fluid, dynamic identity performance that depends on multiple levels of interacting elements in teachers' contexts, and significantly challenges the concept of being embedded in ideas of "best practice." The results of an in-depth qualitative study with seven health and physical education teachers showed that each teacher performed an adaptive multiplicity of self that responded to constraints in each moment of context-specific teaching. The results suggest the need for a reconceptualization of teacher identity that understands it as comprised of many different performances of "teacher" and expressed in context-specific moments of "teacher becoming."