Shared social identifications (family, community, nation, humanity) predict normative actions and psychological well-being, and can be invoked discursively by leaders to mobilise their followers. We illustrate the potential for harnessing shared identities to mobilise resilient public responses against COVID-19. Study 1, a discursive thematic analysis, contrasted Prime Minister Ardern’s use of identity-based rhetoric to mobilise New Zealanders, with Prime Minister Johnson’s use of individualistic appeals to the UK public. Study 2 explored which patterns of social identification predicted protective behaviours (personal hygiene, physical distancing), prosocial actions (helping proximal and distal others), and psychological wellbeing (mental wellbeing, depressive symptoms, anxiety), among 560 UK adults surveyed during lockdown. Our findings suggest how political leaders might beneficially use social identities in communications about extreme events.