Countering the inevitability of communal violence, Amartya Sen defines identities as the product of individual, reasoned choice. Although he acknowledges that such choices are constrained, I argue that Sen’s position overlooks (1) the relational character of identities which reflect caring responsibility rather than autonomous choice, and (2) the power structures that constrain agents’ choices. Using original ethnographic research conducted with women’s peacebuilding groups in India in 2014 and 2015, I develop a theory of identity as performative and grounded in care. Theorizing first from women’s peacebuilding practices and then adding insights from Sara Ruddick’s care ethics and Judith Butler’s theory of performativity, I demonstrate how relationships and structures circumscribe women’s choices, leading them to transform their relational identities rather than choose them after a process of reasoning. Women peacebuilders take up socially-ascribed responsibility for others, building peace relationally as mothers and conflict-affected widows. Post-structural feminism helps us to guard against essentializing these women’s experiences as natural, instead seeing their work as deeply constrained by gender norms even as their peace work transforms those norms. My understanding of identity as relational and performative thus illuminates new sources for and new constraints upon agency.