Research has demonstrated that situational factors such as perceived threats to the social order activate latent authoritarianism. The deadly COVID-19 pandemic presents a rare opportunity to test whether existential threat stemming from an indiscriminate virus moderates the relationship between authoritarianism and political attitudes toward the nation and out-groups. Using data from two large nationally representative samples of adults in the United Kingdom (N = 2,025) and Republic of Ireland (N = 1,041) collected during the initial phases of strict lockdown measures in both countries, we find that the associations between right-wing authoritarianism (RWA) and (1) nationalism and (2) anti-immigrant attitudes are conditional on levels of perceived threat. As anxiety about the COVID-19 pandemic increases, so too does the effect of RWA on those political outcomes. Thus, it appears that existential threats to humanity from the COVID-19 pandemic moderate expressions of authoritarianism in society.