Online learning has experienced rapid growth recently, particularly due to many schools’ closures because of the Covid-19 pandemic. As online learning is growing, institutions have become more interested in knowing what factors influence learners’ satisfaction in online learning environments. This becomes more important for them when the results of studies show lower retention in online courses than in face-to-face traditional courses. Although there is surprisingly little research empirically linking student satisfaction to retention, it is generally believed that there is indeed a positive relationship between the two. The current study was undertaken with 164 online learners at a center of foreign languages in Vietnam. An online survey was administered to assess the participants’ level of satisfaction with their online learning through the four main areas or groups of factors such as course content, teachers, online learning facilities and online learning support. The results revealed that the four groups are significantly associated with learners’ overall satisfaction with online learning, and there is positive retention rate during the program.