ABSTRACT: Previous systematic reviews have examined the efficacy of obesity prevention interventions within early childcare/education settings. Often lacking in these reviews is reporting on external validity, which continues to be underemphasized compared to internal validity. More attention to external validity would help better translate evidence-based interventions to real-world settings. This systematic review aimed to determine the availability of data on both internal and external validity across dimensions of the Reach, Efficacy/Effectiveness, Adoption, Implementation, and Maintenance (RE-AIM) framework in studies reporting on obesity prevention interventions in early childcare/education settings. Inclusion criteria included: randomized controlled trials, early childcare/education setting, targeted children 2-6 years old, addressed both diet and physical activity, collected measures of weight status and diet and/or physical activity, and published within the last 10 years. Searches were conducted in ERIC, PsychInfo, and PubMed; 23 studies met inclusion criteria. A validated RE-AIM abstraction tool was used to code studies. Most commonly reported dimensions were Reach (62.3%), Implementation (53.5%), and Efficacy/Effectiveness (48.7%). Adoption (21.7%) and Maintenance (11.6%) were less often reported. All studies reported on primary outcomes, but few reported on RE-AIM indicators of characteristics of participation and adoption, quality of life, methods used to identify staff, staff inclusion/exclusion criteria and adoption rates, implementation fidelity, measures of cost to start-up and deliver the intervention, and indicators of maintenance. This systematic review underscores the need for more focus on external validity to inform replication, dissemination, and implementation so that evidence-based early childcare/education obesity interventions can be generalized to real-world settings.