The aim of this study is to test a model of online learners' engagement, which integrates social support (from teachers, peers, and family members) and sense of community as direct and indirect factors, with academic self-efficacy playing a mediating role. Survey results based on a questionnaire administered to 255 students enrolled in an online university course confirm, but only partially, our hypothesized model. Path analysis revealed that social support provided by teachers was the only interindividual factor that influenced students' engagement. Moreover, the sense of community was also a significant direct predictor of online learners' engagement. Finally, self-efficacy functioned as a mediator only between the sense of community and engagement.