This paper aims to investigate the identities of pre-service elementary English teachers and factors that affected their identities, especially from the perspectives of in-service teachers. The participants were 18 in-service elementary teachers who were graduate students enrolled in the second language teacher education course taught by the researcher. Pre- and post-survey responses, autobiographic essays, and reflective journals were collected and qualitatively analyzed using content analysis. The findings are as follows: most of the teachers had positive pre-service elementary English teacher identities, whereas some had negative or weak English teacher identities, homeroom teacher identities, and English learner identities. Various institutional factors affected their identities the most, followed by individual and macro-structural factors. Institutional factors were pre-service English teacher education programs, English teaching practicum, native English-speaking teachers, and peer pre-service teachers. Individual factors included the participants’ English skills, English teaching skills, and experiences studying and travelling abroad. Lastly, macro-structural factors covered the Teacher Employment Test and the English subject teaching system. The findings revealed the importance of institutional mediation and human mediation by teacher educators, mentor teachers, and peers in pre-service teacher identity development. Further important implications regarding pre- and in-service English teacher education, development of English teacher identities, and English teachers’ professional development are discussed.