question: The organization of city government into specialized departments allows cities to accomplish an array of service delivery tasks Government reformers argue this fragmentation creates coordination challenges when problems spillover the lines of specialized agencies Functional fragmentation also poses coordination challenges for government communication with the public through social media The global SARS-CoV-2 pandemic and COVID-19 disease provide an opportunity to investigate the consequences of functional fragmentation in city government for social media communication about public health and pandemic response A comparative case analysis of three cities using data from city agency Twitter accounts and key informant interviews demonstrates the consequences of fragmentation for internal coordination, as well as public outreach The experiences of Atlanta, San Francisco, and Washington, DC in the early days of the pandemic provide pragmatic insights for city officials and illustrate the theoretical importance of giving attention to whole of government approaches to city social media communication