Sport is a powerful tool for involving all children – including the most marginalized and vulnerable – in group activities from an early age (UNHCR, 2013). For this reason, sport for development (S4D) organizations use sport as an inclusive means of helping children to improve their health; to develop their physical abilities; to develop their social, educational and leadership skills; and of course, to play and have fun. S4D initiatives come in various forms – from those that build personal and social programmes around sport, to those that include sport as one of many approaches to achieving social goals. This new UNICEF Office of Research – Innocenti summary report analyses available evidence on S4D initiatives for children and youth. The findings cover how the key outcomes of education, social inclusion, protection and empowerment link to sport; what works in practice and how it works; the main challenges for implementation; and recommendations for better policy, practice and research.