This article shows how vulnerable communities use Mexico's Day of the Dead for social justice activism. Activists sustain what I call the ‘political afterlives’ of their victims through street altars and dark humour. I analyse this as a ‘necrosocial repertoire of contention’. The Day of the Dead can play an important role in human rights advocacy by insisting that the marginalised dead be honoured and cared for. However, disappeared people pose a challenge to Mexico's horizontal, or popular, ethics of commemoration and illustrate what I call ‘necrotaboos’, with new problems for the nation's inclusive spirit of commemorating the dead.