In their Facebook profiles, users communicate abundant social comparison information conveying mainly positive self-portrayals. Thereby, social networking sites like Facebook provide a fertile ground for envy. This has been proposed as a mechanism for the potential negative effects of Facebook use on well-being and depression. This article reviews research on this process. Studies show that (especially passive) Facebook use indeed predicts different measures of social comparison as well as envy. In several studies social comparison or envy mediate a positive association between Facebook use and undesirable affective outcomes such as depression. However, causal relationships have not yet been sufficiently established. Methodological and conceptual variety across studies limits their comparability, but reveals viable ideas for future research.