The COVID-19 pandemic presented an opportunity for bordering, that is, for measures that aim to delineate foreigners’ access to citizenship and membership and to further securitize migration policy. Across the globe, new border controls were introduced, stringent new international regulations applied, and hundreds of thousands of flights cancelled, all of which resulted in millions of travelers, including migrant workers and transnational commuters, being stranded. Among the areas affected by these bordering measures is the central Mediterranean migratory route to Italy. In Spring 2020, the Italian government introduced two measures aimed to block migrant arrivals by sea: the closure of ports to search-and-rescue (SAR) operations and the use of ships to quarantine migrants arriving on SAR ships. While the former was only partially implemented and then lifted in the summer of 2020, the latter has become a cornerstone of current securitization policies in Italy. This article — relying on semi-structured interviews with activists, non-governmental organization volunteers, human rights lawyers, and journalists — interrogates the use of quarantine ships during the pandemic as a means of stopping COVID-19's spread by irregular migrants arriving along the central Mediterranean. It shows how this measure, presented as a humanitarian mission to preserve public health, became an opportunity to securitize national and EU borders and how quarantine ships became spaces aimed at filtering and containing arriving migrants. The article aims to contribute to the debate around the bordering policy measures that characterize current EU migration governance and to consider their application during the pandemic.