Background: Out-of-school time (OST) programs are an important setting for supporting student health and academic achievement. This study describes the prevalence and characteristics of school-based OST programs, which can inform efforts to promote healthy behaviors in this setting. Methods: A nationally representative sample of public elementary schools (N = 640) completed surveys in 2013-2014. Administrators reported on OST programs and policies at their school. Multivariable logistic regression models estimated the prevalence of school-based OST programs, adjusting for school characteristics. Among schools with OST programs (N = 475), chi-square tests identified school characteristics associated with having an OST policy about physical activity or nutrition. Results: Three fourths of elementary schools (75.6%) had a full- or partial-year school-based OST program, with 30.8% having both. Full- and partial-year programs were significantly less prevalent in rural and township areas versus urban settings. Only 27.5% of schools with OST programs reported having physical activity and/or nutrition policies. Conclusions: Most US elementary schools have an on-site OST program, but disparities in access exist, and most lack policies or awareness of existing policies regarding physical activity and nutrition. To maximize OST programs' potential benefits, strategies are needed to increase access to programs and physical activity and/or nutrition policy adoption.