Objective: To systematically review the correlates of physical activity and sedentary behavior among children in Early Childhood Education and Care (ECEC) services. Appropriate levels of physical activity and sedentary behavior are important to promote in ECEC services. Methods: A systematic search of 8 databases identified 27 studies published between 1992 and 2015 that met the inclusion criteria. The data were collected and analyzed in 2014 and 2015, and variables were categorized using a Social Ecological Framework. Results: Sixty-six variables were identified. The domains of child characteristics (18 studies) and physical environmental factors (17 studies) were most consistently studied, and, for physical activity had the most positive associations. The strongest associations of physical activity were: child's sex and age, children's gross motor coordination, provision of active opportunities for physical activity, and features of outdoor environments (size, use of and presence). The only strong association for sedentary behavior was the presence of outdoor environments. Conclusion: The correlates of physical activity and sedentary behavior in ECEC services vary. It appears that the most significant influence from within these settings is the physical environments for both physical activity and sedentary behavior. There was an absence of consistent evidence at the educator and organizational levels. Further research in this area should focus on effective use of space, intentional teaching opportunities and well as professional development for educators with an emphasis on their role as a facilitator of quality experiences.