Both practitioners and scholars tend to regard Science and Technology Agreements (STA) to be important, prominent, and highly effective tools for science diplomacy (SD). Yet it is far from clear whether they form an integral part of strategic approaches toward SD or mostly remain rather erratic ad-hoc agreements with more probably vague or even insignificant roles. Based on a working definition of STA, this case-study report offers a mapping of the STA signed by six countries (DK, FR, DE, CH, UK, U.S.) and the European Union between 1961 and 2016. In addition, through a range of expert interviews, it tries to capture practitioners’ views on the role and workings of STA in the realms of international science policy and SD in particular. The research identifies a large increase in the number of concluded STA over time. While some of the countries in the sample studied made extensive use of STA, others were more hesitant or even reluctant to do so. Still, a strong integration of G20-states in a network of bilateral STA can be observed. To illustrate the highly diverse uses and importance of STA, four cases of negotiations that point to their limited strategic use are presented and four types of views or opinions with regard to the uses of STA are identified. Viewed in their respective political context, some apparently erratic STA provisions turn into meaningful strategic instruments. Overall, STA may carry different meanings to different stakeholders engaged in the negotiations; this is why they always serve as boundary objects.