This paper investigates how teachers' professional agency afforded and constrained their decisions to participate in or withdraw from professional learning communities (PLCs). While PLCs are often thought to position teachers as agents, explicit links between teacher agency and key features of PLCs have not been explored. Data from interviews with teachers and principals are examined in relation to five key features of professional learning communities: focus, long-term inquiry, collaboration, leadership support and trust. Three forms of teacher agency emerged in relation to these features and contextual conditions: engaging with communities, abstaining from communities and rejecting communities. Each form of agency has different consequences for sustaining professional learning communities and teacher development.