Science-based issues are crucial to the conduct of foreign policy. Countries large and small, developed and developing, express a clear interest in implementing science diplomacy through politics. This is for the purpose of representation, cooperation, resolving disputes, improving systems, and securing the right to science for citizens and our most vulnerable populations. The same applies to global companies and institutions operating in a complex matrix of technical and relational challenges. This symposium tests this theory against the successes and failures of health diplomacy strategies around two challenging issues: global responses to HIV/AIDS; and harm reduction science linked to lifestyle. Panellists with unique, first-hand insights into real-life best practices and pitfalls encountered in public health service will spotlight how new disciplines and voices are being integrated into decision-making. Accepting that societal problems are not necessarily problems with purely scientific solutions, speakers will argue that meeting global challenges demands not only scientific discovery and innovation, but greater inclusiveness and dialogue. Their common cause is to demonstrate that if we accept the potential of science diplomacy as a common currency capable of underpinning today’s stakeholder interactions, we must equally leverage control at the highest levels to remove the political barriers that prevent affected populations from accessing services.