Scientists were important players in China's Cold War foreign relations. This dissertation examines the international activities of a cohOlt of elite and internationally educated scientists who were involved in international organisations such as the World Federation of Scientific Workers (WFSW) and events such as the Pugwash Conferences on Science and World Affairs. Focusing on the first three decades of the Cold War, this study encompasses a series of critical phases in China's development, in its relations with the outside world, and for its scientific community. Recently declassified archival material covering this period provides an opportunity for a far greater depth of analysis and nuance in understanding than would have been possible less than a decade ago. For the Chinese Communist Party (CCP), these elite scientists were singularly effective intercultural intennediaries who, embedded in overlapping transnational epistemic and activist networks, won sympathy and support for the People's Republic of China (PRC) among foreign intellectuals. Such party-approved propaganda activities also afforded these scientists valuable opportunities to maintain contact with overseas scientific communities from which they were otherwise largely cut off. These PRC-based scientists and the domestic scientific organisations with which they were affiliated all had roles to play within the Chinese foreign affairs system. This dissertation shows that scientists' individual personal and professional networks, their activities in the WFSW, at the Pugwash conferences, and at events like the Peking Science Symposium conferences, all carried a mixture of opportunity and risk for a developing state like the early PRC.