In recent years, digital vigilantism, often dubbed ‘paedophile hunting’, has grabbed media headlines in the US, UK and Europe. Though this novel style of policing carries no legal or moral authority, it is nonetheless ‘taking hold’ within a pluralised policing landscape where its effectiveness at apprehending child sex offenders is capturing public attention. While the emergence of digital vigilantism raises normative questions of where the boundaries of citizen involvement in policing affairs might be drawn, this paper is concerned with firstly, how this kind of citizen-led policing initiative comes into being; secondly, how it emerges as an identifiable policing form; and thirdly, how it acquires leverage and makes its presence felt within a mixed economy of (authorised) policing actors, sites and technologies. The paper sets out a detailed case study of a ‘paedophile hunter’ in action, read through a provocative documentary film, first broadcast on mainstream UK television in October 2014. This lays the groundwork for thinking through the cultural relations of digital vigilantism, and how this proliferating mode of policing practice is engendered and mobilised through affective connectivities, performative political imaginaries and culturally-mediated dialogical praxis. In seeking an entry point for theorising emergent policing forms and their connectedness to other policing bodies, spaces and things, the paper concludes with a thumbnail sketch of assemblage thinking.