Within the field of second language acquisition, pronunciation has received relatively little attention. This lack of research can also be seen in the general lack of systematic pedagogical materials for pronunciation training, effectively reinforcing the "marginalized" nature of pronunciation in the second language classroom (Lee, Plonsky & Saito, 2019). Accordingly, the current study investigated the use of synchronous/asynchronous computer-mediated communication as a method of L2 pronunciation instruction for the phonemic and lexical features of pronunciation. Broadly, the current study examined the effectiveness of face-toface, synchronous, and asynchronous voice computer-mediated communication on EFL learners' pronunciation achievement. In so doing, the study utilized an experimental design with 15 participants in the control group and 30 participants in two experimental groups. There were two types of tests in this study: lexical stress test, and phonemic discrimination test. The results showed the positive effect of CMCoriented instruction compared with F-F instruction on EFL learners' pronunciation development; however, not a significant difference was found between the two CMC instructional modes. The Syn group, on the other hand, tended to vary their ABOUT THE AUTHOR Majid Zeinali Nejad is a Ph.D. candidate in TEFL at Islamic Azad University, Maybod branch. His research interests are language assessment, educational linguistics, and language skills.