The formal sector has professionally managed plastic waste processing in developed countries. In contrast to developing countries like Indonesia, the role of the informal sector dominated the waste management system. Despite having an important role, government policies that explicitly support or optimize the informal sector do not exist. This research studies informal plastic waste management systems. System Dynamics (SD) methodology is used to investigate the structure and influence of the informal sector on the plastic waste management system. The conceptual model has been developed using qualitative phase SD which can be used as a basis in the development of the quantitative phase of SD. This conceptual model supports the development of a valid SD model for evaluating informal plastic waste management policies.