By strengthening urban diplomacy as one of the most important urban management tools, the ground is prepared for the entry of various cities into transnational arenas. Tehran in Iran and Istanbul in Turkey are two examples of cities that are trying to be influential in a larger arena by being members of international institutions and designing global city themes. Therefore, the aim of this article is to make a comparative comparison of urban diplomacy indicators in the metropolitan cities of Tehran and Istanbul. The research method is qualitative. After collecting and classifying information, their analysis was carried out through description and reasoning. From the review of the collected articles, 4 dimensions and 13 indicators were obtained for comparing urban diplomacy. The research findings showed that the situation of Istanbul is more favorable compared to Tehran. Then, using semi-structured interviews, the reasons for Tehran's failure were examined. 6 interviews were conducted and the collected data were analyzed using content analysis. Despite the opportunities and necessities it has had to play an active role in the field of urban diplomacy, the metropolitan city of Tehran has not been able to achieve a suitable position in the field of urban diplomacy due to some obstacles, mainly political. On the other hand, Turkey has adopted neoliberal policies since the 1980s, which has resulted in Istanbul becoming a center for attracting foreign investment. Considering the indicators, it can be said that the dimensions of city diplomacy are interconnected. Therefore, strengthening each of them and removing political obstacles can lead to positive results.