The significance of local actors in regional integration was reaffirmed in November 2018 upon the adoption of the Association of Southeast Asian Nations (ASEAN) Smart Cities Network (ASCN) Framework. The ASCN is envisaged as a collaborative platform where member cities can discuss and resolve the challenges brought about by rapid urbanization. It can thus be said that it fundamentally espouses the role of city diplomacy as an important means and end in the successful realization of sustainable urbanization. In the Philippines’ case, the involvement of Manila, Cebu, and Davao as pilot cities is mainly catalyzed by two factors, namely, the need to address the interests of their communities and as an expression of solidarity with other ASEAN cities. Further, the participation of these local government units (LGUs) in diplomatic activities at the regional level primarily focus on economic, cultural, cooperative, and representative dimensions. To effectively address enforcement-related challenges, LGUs may undertake capacity-building activities, advance a whole-of-society approach, tap new financing schemes, ensure project continuity, and expand the ASCN to include other cities.