This study focused on an EFL writing class via computer-mediated communication (CMC) in an online virtual environment. The purpose was twofold: first to investigate how the constructivist learning theory is perfectly reflected in the online learning environment, and secondly to provide an indepth case study of CMC-based EFL writing instruction. The results indicated that learning EFL writing in a CMC environment fits in with the current trend of constructivist language learning theory and the communicative teaching approach.