Even though the expanding relevance of city diplomacy has unsettled the traditional state-centered conceptualization of international politics, the growing transnational dynamism of city governments is still embedded in, and structurally constrained by, a state-centric international polity. We exemplify this through consideration of Singapore’s exceptionalism as a city-state, and what this means for its capacity for global self-promotion as an urban policy model. When the city-state selectively decides to engage among ‘peer cities’ in city-based institutional venues like city networks, it does so within a hierarchical logic dominated by the political authority and decision-making powers that derive from its capacity for and interest in entertaining relations with other sovereign nation-states. Through a counterfactual logic, Singapore’s outstanding transnational urban position reveals the current constraints of city diplomacy, as other merely city-level governments are compelled to join forces transnationally within a logic framed in terms of (lack of) access to state-centric institutional venues and resources. For the overwhelming majority of city governments, in contrast to Singapore, city networks are obligatory passage points to bypass traditional policy scales. Extending a theoretical bridge between the bodies of literature on urban policy mobilities and city networks, the article excavates Singapore’s ‘privileged’ position to deepen our understanding of the relationship between the city and the state. In doing so, we situate and provide a corrective to overstated narratives of the international rise of cities in the larger contemporary picture of global governance.