The purpose of this qualitative case study was to examine the effect of experiencing computer-mediated peer review (CMPR) on pre-service EFL teachers' writing performance, their peer comments, and their revisions. The study also explored their perceptions of CMPR and computer mediated communication (CMC) features (i.e., "Microsoft Word's" Track Changes and Comments and "Zoom" interaction), implemented in this study, and analyzed their sense of writing self-efficacy after the preparation. This case study involved four pre-service teachers, who were chosen from a writing class of 34 students, and their writing instructor (for interview only), through a purposive sampling. These pre-service teachers were also second-year English majors attending a four-year program of the faculty of Education at a public university in Northeastern Thailand. The qualitative data were collected from pre- and post-tests (i.e., the students' first and second drafts), pre- and post-questionnaires, and interviews. The findings of this study indicated that CMPR is an effective approach to improve pre-service teachers' writing ability, enhance the quality of their peer comments (i.e., peer-oriented comment revisions), and increase the number of peer-oriented comment revisions. Further, all pre-service teachers had positive attitudes towards CMPR. They self-reported that this CMPR writing experience was useful and fun. Their sense of writing self-efficacy increased through the CMPR activity. The findings of this study suggested that teacher preparation programs and writing instructors should provide as much background knowledge of essay writings (e.g., a five-paragraph essay structure) and technology applications in pre-service coursework (i.e., writing) as needed for future classroom application. Pre-service teachers should also be taught how to organize the essay and how to provide constructive feedback to their peers to be capable of giving it to their future students. Although the university in this study does not offer online courses and programs for pre-service teachers, the curriculum should prepare these future teachers with sufficient and various writing experience in both traditional face-to-face and online forms, so they can transfer and apply them into their future classroom instruction and pedagogy. [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.]