Science diplomacy has played an important role in Chinese history, including in the history of science and technology (S&T) development. While we may consider science diplomacy as simply a part of China's Reform and Opening-up policy, the fact is that even in the Kuomintang period (1925–1949) or the Maoist period (1949–1976) it was a key element of Chinese foreign relations. The targets and nature of science diplomacy were shaped by the prevailing politics and economic issues of the times. For example, the Cold War limited the breadth and depth of S&T cooperation between China and the West. Nonetheless, the People's Republic of China pursued cooperation with the Soviet Union and newly independent countries in a very steadfast manner and continues to engage with Russia and developing countries today. This article analyses the nature of science diplomacy as an element of both China's S&T development and its foreign relations. The interactions and practices at the intersection of science and foreign policy in China are manifold. In addition to providing a comprehensive overview, this article also highlights evolving trends, especially in terms of the deepening of China's linkages across the international S&T system. Finally, the article examines the recent impact of the apparent rise of techno-nationalism and how this has affected the nature of China's international S&T activities regarding Beijing's use of science diplomacy.