Worldwide, conservation initiatives have attempted to curb illegal harvest, use and trade of marine turtles at least since the 1950s. Despite some declines in local trade and consumption, these illegal activities are still often reported as a key threat to marine turtle populations. Reassessing and refining global conservation priorities for marine turtles allows us to formulate evidence-based strategies and effective interventions to address this threat. We surveyed a total of 103 marine turtle conservation researchers and practitioners globally to understand how conservation efforts can be better allocated to curb illegal harvest, use and trade. We explored the characteristics of these illegal activities, conservation priorities, challenges and lessons learnt. According to participants’ perceptions, progress has been achieved, but illegal harvest, use and trade remain pressing threats globally. Current challenges to addressing illegal activities relate to fisheries management, enforcement and legislation. Recommended priority actions include law and penalty enforcement, enhancing environmental literacy, awareness and stakeholder participation, and improving local conservation leadership and onshore/maritime management based on research. Based on participants' perceptions, we identify priorities for marine turtle conservation interventions that aim to curb illegal harvest, use and trade. Given the challenges of obtaining reliable information on sensitive topics such as illegal harvest, use and trade, further work should seek to validate our findings through empirical research. Further work could also seek to comprehend better how expert elicitation in conservation is influenced by individual experience, perspectives and goals.