This qualitative study investigated the professional identities of four mainstream teachers of English learners (ELs). Four teachers in two school contexts (urban and suburban) were interviewed five times and observed during formal instruction four times. Adopting a sociocultural perspective on identity, the study employed discourse analysis to answer the research questions: (a) what are the professional identities of four mainstream teachers of English learners in Northern New Jersey schools; (b) in what ways are these identities constructed by the participants; and (c) what seem to be the influences on these teachers' professional identities? The interview data were analyzed using three of Gee's (2011b; 2011c) building tasks of language: relationships, politics, and identities. Observations were coded using open and axial coding. Findings suggest that despite differing identity conceptions, making ELs comfortable in the classroom, students' English language acquisition, and inclusion in academic activities were central elements in the professional identities of all of the participants. Relationships with students, parents and families, colleagues, and former teachers emerged as influences that supported the enactment of professional self. Linguistic, cultural, and national identities surfaced as having differential influence on the professional identities. Despite differences in their constructions of professional self, the teachers' reported enactments of their identities in interviews and within the context of formal instruction were more similar than different. That is, there was greater variation in the enactment of professional self in the context of informal instruction and engagement with members of the school community other than students than during formal instruction. Differential constructions of linguistic, national, and cultural identities in relation to teacher identity emerged even among teachers of the same social and cultural backgrounds. While affirming ELs' inclusion in the classroom through efforts to make students feel comfortable was important to all participants, they struggled with identifying research based pedagogical practices to promote (rather than solely include) ELs in the classroom. The findings reaffirm the need for a teacher workforce that identifies as linguistically responsive. A consideration of these findings in relation to the research literature is discussed along with recommendations for teacher education practice and teacher education research. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]