Science diplomacy is often portrayed as a neutral and universal tool for peace and international cooperation; however, this optimistic narrative fails to explain the deep structural inequalities in the production and distribution of knowledge. This study aims to deconstruct this narrative and propose a critical model by examining the nature of science diplomacy as a “circuit of culture” imbued with power relations. Using a systematic review and interpretive synthesis of 20 selected studies (2000–2025), and drawing on Stuart Hall’s “Circuit of Culture” theoretical framework and post-colonial approaches, the findings reveal that inequality is reproduced at three levels. At the macro level (encoding), policies are influenced by geopolitical interests and “Global North” hegemony, which views the South merely as a consumer. At the meso level (circulation), linguistic imperialism of English and the gatekeeping of prestigious journals hinder the dissemination of indigenous and non-Western voices. At the micro level (decoding), scientists face identity challenges, stigma, and the emotional costs of mobility, forcing them to negotiate within a “Third Space” between indigenous identity and imposed standards. The conceptual model of the study demonstrates that current science diplomacy, rather than being an equal dialogue, is a process of systematic exclusion and epistemic violence. Realizing the true potential of this field requires a shift from the “soft power” paradigm to “epistemic justice” and the recognition of pluralism in the global scientific system.