This qualitative study seeks to understand how English teachers in Korean secondary schools develop their language teacher identities through their personal and professional experiences as they teach, learn, and live in the unique sociological context of South Korea. Merging multi-case study method with narrative inquiry framework, it analyzed the narratives of language teacher identity (LTI) formation process from Korean secondary school English teachers (KSSET), their past and present as well as of the future prospect as a language professional. Although there has been burgeoning field of research on LTI in language teacher education, and second language acquisition (SLT) in global scholarship, few studies have examined the KSSETs' professional identity formation using the teachers' voices. The study attempted to extend the existing knowledge and theory basis related to diverse LTI formation of English teachers in different places in the globe. The analysis drew the following conclusions: (1) KSSET early experiences are context-bound and foundational in their career choice, (2) overseas learning was a transformative experience for pre-service LTI, (3) KSSET LTI is challenged and negotiated by competing English language teaching practices and multiple roles coupled with conflicting emotions, and (4) KSSET's identity is an ongoing journey. Also, articulation of the LTI development process of this group -- their learning and teaching, struggles and agencies, and perceived meanings of their profession from the teachers' own points of view -- indicated some implications for language teacher educators and administrators in South Korea as well as in other relevant contexts. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]