The challenge for a circular plastics economy transition is to focus policies on key leverage points that initiate actual system transitions. This requires a systemic perspective on the plastics industries. This study takes such a systemic perspective by employing a network approach to examine the often-underestimated complexity of interrelating markets in a circular plastics economy, and their structural sensitivity to governance interventions. Based on the case of polyethylene terephthalate (PET) markets in Germany, we investigate the structures and underlying dynamics of increasing circularity in the PET industry. Concerns about plastic litter accumulating in the natural environment have facilitated the development of niche markets for the recycling of plastic litter recovered from the environment. We systematically reveal that recycling markets connecting diverse waste sources with a broad range of new applications are key areas of intervention in the structural transitions towards circular industries. By connecting otherwise disconnected parts of the system, the recycling of recovered plastic litter is a key leverage point for the circular economy transition. We recommend to focus governance efforts on such key leverage markets as powerful venues to initiate systemic change.