This study attempts to identify the specific professional needs of pre-service English immersion teachers in Korea in order to establish key components of English immersion teacher preparation programs. As an alternative approach of English language education, immersion instruction has been employed by a number of private and public schools in different forms in Korea. It is believed that learning subject matter in English will increase students' motivation and in turn improve their English language proficiency. The key to the successful implementation of immersion instruction is an adequate supply of qualified teachers who are linguistically competent as well as suitably trained to teach subject matter in English. However, little is known about the particular level of expertise of English immersion teachers in Korea. This research delves into the perceptions of experienced English immersion teachers by exploring their own experiences with respect to both their training and teaching in public elementary schools. The data were gathered through on-line surveys and in-depth interviews from the participants who worked as immersion instructors under an experimental educational system organized by a local educational bureau. Both quantitative and qualitative analyses were employed to evaluate the data. A thematic analysis was conducted for the narrative analysis of the participants' accounts; specifically, six phases of an analytic process suggested by Braun and Clarke (2006) were applied. Experienced teachers' perceptions gained through firsthand experience provide an ideological foundation for the professional needs of English immersion teachers. Furthermore, the findings contribute to a determination of the essential features of teacher preparation programs for English immersion instruction. The findings include the characteristics, problems, advantages, and significant challenges of English immersion instruction, training experiences of the participants as well as their suggestions for what particular training is required for pre-service immersion teachers. In the discussion, based on the findings, potential educational elements regarding future training programs for pre-service English immersion teachers in Korea are identified. The major components entail immersion theory and pedagogy, experienced teachers' cases, standard instructional models, language training, TSG, and field experience, among others. Furthermore, in addition to the significance of the supply of qualified immersion teachers to ensure the effectiveness of immersion instruction, establishment of an ideal immersion model that fits well with the English language education environment in Korea was also acknowledged as critical. [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.]