Public authorities have traditionally used an official language style in public, but currently social media have become an outlet for humour. This article uses positioning analysis to discuss challenges that use of humour poses for the identity of public organizations. Drawing on interviews with communications professionals working in the emergency services sector, the article suggests six evaluative themes that factor into organizational identity construction, such as the frequency and type of humour in social media posts. Indeed, while humour helps fashion more flexible and risk-taking organizational identities, it can also stand contrary to a bureaucratic ethos of public servantship and equal treatment. Dilemmas thus arise for public authorities that seek to adjust to the times and still remain ‘in character’. The article contributes to organizational identity research by considering the hitherto overlooked immersion of social media use, humour and organizational identity formation.