Contemporary scholarship concerning science diplomacy is increasingly taking a historical approach. In our introduction to this special issue, we argue that this approach promises insight into science diplomacy because of the tools historians of science bring to their work. In particular, we observe that not only are historians of science currently poised to chart the diplomatic aspects involved in the transnational circulation of technoscientific knowledge, materials, and expertise. They are ready to bring critical global analysis to an important phenomenon that has too often been treated as a benign diplomacy device deployed by the Global North without equal reference to the Global South. Through cases discussed in the articles of the special issue, however, we see that historically, in the Global South as well as the Global North, science diplomacy has often functioned to mediate the circulation of technoscientific knowledge and materials, and its historical study helps to better illuminate the resulting knowledge‐power nexus.