This meta-analysis reports on the effectiveness of targeted interventions focusing on child care professionals to improve child care quality, caregiver interaction skills, and child social-emotional development. Within randomized controlled trials, interventions are moderately effective in improving overall caregiver-child interactions (k=19, Hedges' g= 0.35) and in improving child care quality on the classroom level (k=11; Hedges' g=0.39), the caregiver level (k=10; Hedges' g=0.44), and the child level (k=6; Hedges' g= 0.26). Based on these findings, the implementation of evidence-based targeted interventions on a larger scale than currently exists may lead to better social-emotional development for children under the age of 5 years. There remains, however, an urgent need for more and larger randomized controlled trials with a solid design and high quality measures in order to shed more light on which child care components for which children are most critical in supporting children's socio-emotional development. (author abstract)