Science diplomacy has caught remarkable attention in public policy and academic research over the last fifteen years. However, the concept is plagued by a huge talk–action discrepancy: its public discourse has reached a problematic state of dazzling self-adulation, while it is unclear if and how the actual policies and associated organizations live up to these expectations. The article reconstructs three structural causes to explain the recent hype about science diplomacy. It further encourages actors to organize evaluations that ask whether and how actions of science diplomacy can be valuable. In this regard, a first set of fundamental principles is proposed for setting up an evaluative framework. In conclusion, the article advises science diplomacy actors from democratic states and institutions, from both academic research and public policy, to stop dreaming about soft power influence on authoritarian states and regimes but rather face new geopolitical realities.