Urban cultural diplomacy, particularly through the mechanisms of Sister City Agreements, has gained increasing prominence as an effective instrument in fostering international relations, promoting intercultural interactions, and strengthening a nation's soft power. This research aims to provide a conceptual framework for urban cultural diplomacy, with an emphasis on sister city relationships, by exploring the theoretical and empirical dimensions of this concept. Accordingly, the study's theoretical framework is grounded in the analysis of key theories including People-to-People Diplomacy, Cultural Identity, Social Capital, Multi-Level Diplomacy, Local Economic Cooperation, Peacebuilding, Glocalization, and Knowledge and Innovation Exchange. These theories suggest that urban diplomacy can not only strengthen cultural ties but also contribute to economic development, enhance social capital, and mitigate international tensions. The research methodology is based on a library research approach and secondary analysis of scholarly sources and previous studies in the field of urban cultural diplomacy. The findings indicate that Sister City Agreements/Partnerships provide a suitable platform for enhancing scientific, educational, cultural, and economic collaboration between different communities. An examination of international experiences, particularly the case studies of cities such as Paris, New York, Barcelona, and the Chinese model of urban diplomacy, demonstrates the significant impact of this type of diplomacy on international politics. The results suggest that Iran, by leveraging the rich cultural - historical Geographical potentials of its cities, can utilize urban diplomacy as a tool for strengthening international relations and intercultural interactions. However, the formulation of coherent strategies and planning are essential for the optimal exploitation of these potentials