Drawing on interactionist and socio-cultural theories, tools provided in computer-mediated communication (CMC) environments have long been considered able to create an environment that shares many communicative features with face-to-face communication. Over the past two decades, researchers have employed a variety of strategies to examine the asserted advantages and possible limitations of learning a second language in such a computer mediated environment. Despite its seeming appeal to language educators, the literature on the effectiveness of CMC in SLA is unable to conclusively support its benefits. This meta-analysis aims to systematically synthesize findings from (quasi-) experimental studies conducted between 2000-2012 to examine whether there was a link between the use of CMC and second language acquisition (SLA). Results from 59 primary studies show a positive and medium effect from CMC interventions. Additionally, communication taking place either asynchronously or synchronously does not seem to have a differential effect on SLA. Furthermore, learners' proficiency level, interlocutor type, research context and task type were found to be variables that would significantly moderate the effectiveness of interaction in such an environment. The above results, however, were interpreted as tentative due to the small n-size of some categories of variables under comparison.