Plastics leakage has become a pressing issue for many developing countries. While a number of development co-operation initiatives with a focus on tackling plastic pollution have recently emerged, there is currently no comprehensive assessment of the volume and scope of international development co-operation in this area. This report contributes to fill this gap by bringing together OECD’s unique statistical sources and expertise. First, this paper assesses the scale of the plastic pollution problem in developing countries by providing evidence on developing countries’ plastic use, waste, and leakage volumes, and assessing the specificity of plastics-related impacts in developing countries. Secondly, it quantifies development co-operation support in this area through a refined methodology developed as part of the OECD Sustainable Ocean for All Initiative. Finally, the paper presents innovative development co-operation approaches that are helping developing countries to scale up financing and impact of waste management projects.