This study investigates how an elementary-level content classroom teacher and an elementary-level ESL teacher in a metropolitan region in Massachusetts negotiated teachers' identities and identity dissonances in teachers' attempt to advocate for emergent bilinguals. Using critical discourse analysis of qualitative data, this study examines the cognitive, emotional and social dimensions of teacher advocacy identity negotiations. Furthermore, the current study illuminates two teachers' different ways of negotiating with advocacy identity dissonances, dependent on teachers' sense of agency and affordances in their social identity positionings and working contexts. The findings point to the importance of using teachers' identity dissonances as a tool to develop teachers' agency and enact advocacy actions. Specific suggestions are made for preparation and professional development of teachers of emergent bilinguals in the fields of language teacher education and teacher education in general.