Background: There is a growing body of research and evidence for the efficacy of Internet-based eating disorder (ED) prevention interventions for adults. However, much less is known about the reach, adoption, implementation and maintenance of these interventions. The RE-AIM (reach, efficacy/effectiveness, adoption, implementation, maintenance) model provides a framework to systematically assess this information. Methods: A literature search was conducted in PubMed, Web of Science and PsycINFO for articles published between 2000 and 2019. Additionally, reference lists of the studies included and existing reviews published until the end of 2020 were searched. Sixty original articles describing 54 individual studies fulfilled inclusion criteria. Data were extracted for a total of 43 RE-AIM indicators for each study. Fostering and hindering factors for reach, adoption, implementation and maintenance were assessed qualitatively. Results: Overall reporting rates were best for the RE-AIM dimensions reach (62.6%), implementation (57.0%) and effectiveness (54.2%), while adoption (24.2%) and maintenance (21.5%) had comparatively low overall reporting rates. Reporting on indicators of internal validity, such as sample size, effects or description of interventions was better than indicators relevant for dissemination and implementation in real-world settings, e.g. characteristics of non-participants, characteristics and representativeness of settings, and data to estimate cost. Conclusions: Because most Internet-based ED prevention interventions are provided in a research-funded context, little is known about their public health impact. Better reporting of factors determining external validity is needed to inform dissemination and implementation of these interventions.