Because transnational environmental crime (TEC) can result in the demise of an environmental resource or irreversible damage to the environment and has implications for national and global security, its prevention is a critical issue. Deterrence through law enforcement can go only a limited distance towards preventing TEC. However, there is a huge potential for third parties to be active participants, alongside governmental authorities, in crafting and implementing strategies for TEC prevention. This article explores the ways in which states can catalyze third parties – non-state, non-offending actors – to contribute their own capacities towards the pursuit of preventive outcomes. It draws together concepts and theories from policing studies, criminology and regulatory studies to highlight changing relationships between the state and non-state actors with respect to crime control, and applies them to TEC. Examples and illustrations used in the article relate mainly to efforts to combat the illegal wildlife trade. The article concludes that a more systematic approach to TEC prevention involving third parties is needed, and that this requires dedicated strategic analysis and planning on the part of states, working individually and together.