Since Seoul participated in the WHO Healthy Cities Network in 2004, and the Korea Healthy Cities Partnership (KHCP) was established in 2006, healthy cities have grown quantitatively as well as qualitatively. However, as COVID-19 spread rapidly globally in 2020, the vulnerability of large cities has been greatly exposed. Against this backdrop, the purpose of this study was to evaluate the COVID-19 responses of healthy cities of Seoul as well as self-governing districts (GU), based on the WHO European Healthy Cities Network. As a result, strong leadership, dedicated organization and manpower from the perspective of precondition, community resilience response, support for mental health, as well as stigma and discrimination in respect to activities, are needed. Also, the result showed that infectious disease stemmed from social factors, which was translated into the need of the community environment to respond to infectious diseases. Last, we suggest a new healthy city paradigm while maintaining the areas of physical activity and chronic disease management, encompassing the vulnerability revealed by COVID-19 and a joint response agenda for climate change: 1) enhancing physical activity and strengthening chronic disease management, 2) reinforcing the ability to respond to infectious disease, 3) reinforcing mental health and psychological support systems, 4) improving response to climate changes, 5) reinforcing participation and cooperation.