When responding to a public health crisis such as an infectious disease, various public health services and activities that were regularly performed are affected. The damage to the basis of the public health system makes it difficult to recover to the state before the outbreak. Characteristics of the megacity Seoul— high population density, large floating population, and active and intense social, economic, and cultural exchange globally—could be a trigger for the transmission of the infectious virus, and the damage could be lethal when an infectious disease occurs. In order to minimize damage to citizens and the city as a whole in case of new infectious disease occurrence, it is necessary to analyze the achievements and limitations of COVID-19 response process of Seoul at various level. So we reviewed and evaluated the outcomes and problems of the COVID-19 management systems in other metropolitans. We also conducted online surveys three times for general citizens, and interviewed various stakeholders including public officials and public health experts. During one year of the COVID-19 pandemic, people in Seoul had to live through rigorous social distancing measures in their daily life, and their psychological and mental health became worse. Based on the results, we discussed the epidemiological investigation system, support plans for the vulnerable class, personal information protection, and the role and function of the Seoul Infectious Disease Research Center.